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Field Measurements on Multi-year Ice in the Beaufort Sea,

August 2011

M. Johnston

Technical Report, CHC-TR-083

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Field Measurements on Multi-year Ice in the Beaufort Sea,

August 2011

M. Johnston

Canadian Hydraulics Centre National Research Council of Canada

Montreal Road Ottawa, Ontario K1A 0R6

FINAL REPORT prepared for:

Imperial Oil Resources Ventures Ltd. Calgary, AB

University of Manitoba Winnipeg, Manitoba

Technical Report, CHC-TR-083 November 2011

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The thickness, strength, salinity and temperature of two, drifting multi-year ice floes in the Beaufort Sea are presented here. Although only two floes were sampled during the two-week voyage on the CCGS Amundsen, the floes characterized a wide spectrum of multi-year ice. Floe B1S1 (74.8°N, 128.3°W) originated from the landfast multi-year hummock field off Prince Patrick Island, 250 km to the northeast. Drill-hole measurements revealed ice thicknesses from 3.6 to 9.3 m, for an average floe thickness of 7.2 m (±1.4 m). The ice was quite warm, saline and weak. The uppermost 3 m of ice had an average temperature of -0.9°C and an average salinity of 1.8‰. The average borehole strength of the 7 m thick ice at the two tested boreholes was 7.3 MPa and 4.5 MPa. A total of 10 controlled ship impacts were conducted with Floe B1S1, during which time the ship penetrated several lengths into the floe.

Floe B1S2 (75.0°N, 129.0°W) had drill-hole thicknesses from 5.1 to 15.7 m, and an average thickness of 8.0 m (±2.3 m). The hummocked feature that was tested on this floe was thicker, colder and less saline than the ice tested in Floe B1S1. The uppermost 7 m of the hummock had an average temperature of -2.6°C, an average salinity of 1.0‰ and an average borehole strength of 22.0 MPa. It is not surprising then, that the CCGS Amundsen responded very differently to controlled impacts with Floe B1S2. The first three rams produced just a small imprint in the floe edge; the fourth and final ram caused a crack to propagate by exploiting local weaknesses in the ice.

It should not be surprising that the Beaufort Sea pack ice consists of floes with great integrity and relatively weak floes. Different types of floes can, and do, occur in close proximity to one another. Floes that circulate in the Beaufort Gyre for many years become weathered and consolidated. Floes that have been recently deformed, such as Floe B1S1, may be thick, but are not as consolidated. Variable types of ice in the Beaufort Sea were also encountered in August 2009: Barber et al. (2009) noted that the CCGS Amundsen operated in extensively decayed ice on 31 August, yet the CCGS Louis S. St-Laurent encountered a 10 km diameter multi-year floe in the southern Beaufort Sea on 8 August 2009, that the ship spent two hours ramming (B. Molyneux, personal communication from Canadian Ice Service) before it could turn out of the floe.

Results from the companion study of the ice impact forces on the CCGS Amundsen when ramming Floe B1S1 and Floe B1S2 will be presented in a separate report. The ice thickness comparison of the drill hole measurements, ice-based electromagnetic (EM) sensor and airborne HEM sensor will be published by University of Manitoba at a later date.

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Table of Contents

Abstract ... 5 Table of Contents... 2 List of Figures ... 3 List of Tables ... 5 1.0 Objectives ... 1

2.0 Voyage of CCGS Amundsen during Leg 2A ... 2

3.0 Methodology ... 5

3.1 Floe Selection and Access ... 5

3.2 Ice Property Measurements ... 6

3.3 Drill Hole Technique ... 7

3.4 Electromagnetic (EM) Induction Sensors... 8

4.0 Results from Field Studies ... 9

4.1 Floe B1S1: Aug 15, 16... 9

4.1.1 Surface and bottom topography along drill hole transects ... 13

4.1.2 Temperature, salinity and strength of Floe B1S1 ... 13

4.1.3 Ship impact tests with Floe B1S1 ... 17

4.2 Floe B1S2: Aug 17 – 18... 20

4.2.1 Surface and bottom topography of Floe B1S2... 22

4.2.2 Temperature, salinity and strength of Floe B1S2 ... 22

4.2.3 Ship impact tests with Floe B1S2 ... 27

5.0 Conclusions... 29

5.1 Multi-year ice thickness by direct drilling... 29

5.2 Temperature, Salinity and Strength of Sampled Floes ... 30

6.0 Recommendations for future Beaufort Sea Field Programs ... 31

7.0 Acknowledgments... 32

8.0 References... 32

Appendix A: Drill holes in flagged transects... 1

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List of Figures

Figure 1 Location of sampled multi-year ice floes ... 1

Figure 2 Voyage of the CCGS Amundsen during Leg 2A ... 3

Figure 3 Accessing Floe B1S2... 6

Figure 4 NRC dual acting borehole indentor... 7

Figure 5 Floe S1B1 as identified from satellite imagery ... 10

Figure 6 Aerial perspective of ship secured to Floe S1B1 in an open water lead ... 10

Figure 7 Trajectories of the ship and Floe B1S1 from 14 to 16 August... 11

Figure 8 Floe B1S1: (a) strength tests in two boreholes (b) surface topography ... 12

Figure 9 Profile view of Floe B1S1: topography and bottom ice surface ... 14

Figure 10 Cores from borehole #1 (a) uppermost 0.6 m of ice and (b) depths 2.7 to 3.0 m ... 16

Figure 11 Temperature, salinity and strength profiles of Floe B1S1... 17

Figure 12 Ship track showing 10 rams conducted with Floe B1S1... 18

Figure 13 Bow prints caused by (a) first ram and (b) last ram with Floe B1S1 ... 19

Figure 14 Floe S1B2 as identified from satellite imagery ... 20

Figure 15 Aerial perspective of ship secured against Floe S1B2 ... 21

Figure 16 Trajectories of Floe B1S2 during two days of on-ice measurements... 21

Figure 17 Floe B1S2: (a) drill-holes and (b) hummock on which measurements were made... 24

Figure 18 Floe B1S2: Profile view of surface and bottom topography ... 25

Figure 19 Temperature, salinity and strength profiles of Floe B1S2... 26

Figure 20 Ship track showing four rams conducted with Floe B1S2 ... 27

Figure 21 Bow prints caused by (a) first ram and (b) last ram with Floe B1S1 ... 28

Figure 22 Comparison of five years of drill hole measurements on multi-year floes ... 29

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List of Tables

Table 1 Multi-year floes sampled during Leg 2A... 2 Table 2 Summary of ice thicknesses measured on Floe B1S1 ... 13 Table 3 Summary of ice thicknesses measured on Floe B1S2 ... 25

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Field Measurements on Multi-year Ice

in the Beaufort Sea, August 2011

1.0 Objectives

The thickness, strength, salinity and temperature of deformed multi-year floes in the Beaufort Sea were measured by the National Research Council’s Canadian Hydraulics Centre (NRC-CHC) for this jointly-funded study. Of particular interest to the Joint Participants, were the so-called Potentially Unmanageable Ice Features (PUIFs) which, by definition, include highly deformed, thick multi-year ice floes that likely would be unmanageable when using an icebreaker to defend a hydrocarbon installation. The investigation took place from the CCGS

Amundsen during Leg 2A (11 to 25 August 2011). One of the reasons that the month of August was selected as the timeframe for the program was because, at that time of year, the near absence (and weakened state) of first-year ice greatly improve a ship’s ability to access multi-year floes. Two multi-year ice floes were sampled during the two-week field program, as shown in Figure 1. The particulars of the two sampled floes are listed in Table 1. Here, it should be noted that ice property measurements made during this field program represent late-summer conditions only; the same floes would have had much higher strength (and potentially greater thickness) had they been sampled in winter, spring or early summer.

Floe B1S1 (15, 16 Aug) Floe B1S2 (17, 18 Aug) Banks Island Viscount Melville Sound Beaufort Sea Prince Patrick Isl Sachs Harbour 10/10ths Old Ice Concentration 9 to 9/10ths 7 to 8/10ths 4 to 6/10ths 1 to 3/10ths <1/10th “Box 1”

Figure 1 Location of sampled multi-year ice floes and “Box 1”, the initially selected study area

Map shows only the old ice concentration for 15 August, based upon CIS Regional Ice Chart. Polygons were combined to obtain the concentrations in the legend, as shown by outlines in yellow areas (4 to

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Table 1 Multi-year floes sampled during Leg 2A

Floe ID floe size, estimated from satellite imagery date sampled initial position (N, W) final position (N, W) on-ice sampling period (hrs) total drift (km)a avg. drift speed (km/hr) Floe B1S1 37 km x 46 km 15 Aug 74.8567 128.3223 74.8511 128.2709 7.2 1.8 0.25 Floe B1S1 37 km x 46 km 16 Aug 74.8312 128.2030 74.8268 128.1290 6.1 2.3 0.38 Floe B1S2 6.5 x 6.5 km 17 Aug 75.0274 128.9756 75.0203 128.9464 4.7 1.2 0.25 Floe B1S2 6.5 x 6.5 km 18 Aug 74.9816 128.8825 74.9644 128.8618 7.8 2.1 0.27 a

total drift of floes during NRC-CHC on-ice measurements, as obtained from the ship/floe trajectory logged by GPS

2.0 Voyage of CCGS Amundsen during Leg 2A

On 11 August, most scientific personnel joined the flight chartered for Coast Guard crew change operations, from Quebec, QC to Kugluktuk, NWT. The plane landed in Kugluktuk early on the afternoon of 11 August, after which many hours were spent transferring crew and luggage to the CCGS Amundsen. By 19:00CT1, the ship was underway for the study area in the Beaufort Sea (blue box shown in Figure 2-a). First ice was encountered on 13 August at 07:00CT (72°45.7N, 128°33.5W). At 12:00CT, the Captain took the opportunity to impact a few of the more substantial looking floes in the area, for the benefit another jointly-funded project undertaken by NRC-CHC. That project involved measuring global ice impact forces on the ship using a specially developed inertial measurement system called MOTAN. The ship impact forces will be the subject of a separate report entitled “Measuring Global Ice Impact Forces on the CCGS

Amundsen” (Johnston, in preparation) to be submitted to Canadian Coast Guard, ArcticNet-Imperial Oil Research Venture Limited (IORVL) and the University of Manitoba in March 2012.

Upon departing Kugluktuk, the ship proceeded to sail 900 km north to a sampling area designated as “Box 1” (Figure 2-a), an area of interest that the Participants had previously selected from satellite imagery. Box 1 was about 20 nmi by 25 nmi (37 km by 46 km), with its central point at 72°56’N, 129°19’W (Brovin and Turnbull, 2011). This region was situated near the eastern edge of the Beaufort pack ice where the concentration of old ice was from 4 to 6/10ths (Figure 1) with lesser amounts of thick first-year ice and/or open water. The total ice concentration in that area ranged from 7 to 9/10ths.

1

The ship was on Central Time (CT) during Leg2A of the voyage. Both Central Time and UTC (CT + 6 hrs) are used in this report.

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11 Aug 19:00CT depart Kugluktuk 12 Aug 12:00CT 13 Aug 00:00CT 13 Aug 12:00CT 14 Aug 00:00CT 14 Aug 12:00CT 21 Aug 12:00CT 15 Aug - 20 Aug (sample floes B1S1 & B1S2) 22 Aug 00:00CT 23 Aug 00:00CT 23 Aug 12:00CT 24 Aug 00:00CT 24 Aug 12:00CT 25 Aug 00:00CT 25 Aug 12:00CT

Figure 2 Voyage of the CCGS Amundsen during Leg 2A

(a) from 11 to 20 August and (b) from 22 to 25 August

The marginal floes in the area that was pre-selected based upon satellite imagery (blue box) were abandoned in search of more competent floes further north, two of which were sampled (green stars)

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The floes that had been targeted inside Box 1 from satellite imagery were found to be too small and weak for on-ice operations. For this field program, the floes needed to be solid enough to hold the ship securely throughout two days of on-ice measurements. The technique of using the ship itself to assess the quality of the ice was used: the floe was considered unsatisfactory if it split during impact, if the ice cusps overturned by the ship were too thin and/or if the ice presented minimal resistance to the ship. None of the floes in Box 1 were considered satisfactory. Neither could tracking beacons be deployed on the floes since the floes were expected to fracture in the near future, causing the beacons to be lost prematurely.

Faced with this reality, the decision was made to proceed 200 km north (Figure 2-a) to a region where satellite imagery, and the Chief Scientist’s past experience, suggested more substantial floes existed. Indeed, the two floes that were sampled during the field program were located in that area, about 100 to 150 km from the northwest coast of Banks Island (two stars shown in Figure 2). Those two floes were sampled from 14 August to 18 August.

An unfortunate incident occurred on the ice on 18 August, just after scientific personnel and their equipment had returned from Floe B1S2. The incident was deemed to have placed the health and safety aspect of the on-ice program in jeopardy. As a result, all on-ice activities were terminated on 19 August. At the very same time, a storm was taking shape elsewhere in the Beaufort Sea. On 20 August the ship departed the sampling area and sailed approximately 150 km to the north-west coast of Banks Island; it was thought prudent for the ship to take shelter from the storm. The ship remained off the coast of Banks Island until the storm passed. On 23 August, the same region of ice in which the two floes had been sampled was re-visited (Figure 2-b), to examine the effect that the storm had upon the ice conditions, and to conduct ship-based science activities. The ship departed the area on 24 August for the journey to Sachs Harbour.

The ship arrived at Sachs Harbour on the morning of 25 August, after which began the long process of transferring scientific personnel and their luggage by helicopter. Most of the scientific personnel had been transferred to Sachs Harbour by afternoon, when the weather closed in. This not only prevented the scheduled charter plane from landing, it prevented the ship’s helicopter from being used to return personnel and luggage to the ship. As a consequence, all personnel and gear were transported from the Sachs Harbour airport to the beach, where the Coast Guard’s barge transported them back to the ship. A second scientific crew change was attempted by helicopter the following day (26 August). Thankfully, the weather cooperated and all personnel departed Sachs Harbour at 22:00CT.

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3.0 Methodology

The NRC-CHC on-ice field team consisted of four people, which is the minimum number of people required for two teams to work on the ice, relatively independently. Three of the field participants were from NRC-CHC and the fourth person participated as part of University of Manitoba’s in-kind contribution to the project. Following is a brief description of how floes were selected, how they were accessed, and the methodology that was used to sample the floes.

3.1 Floe Selection and Access

To be a satisfactory candidate for on-ice measurements, a multi-year ice floe needed to survive the ship-penetration test, to provide a reasonably straight edge against which to secure the ship, and to pass a preliminary on-ice examination of the ice surface. The on-ice assessment was done by holding the ship fast against the floe edge as the Chief Scientist, and two or three crew members, were delivered to the floe in the ship’s over-the-side basket. The Chief Scientist walked around on the floe, about a ship-length or so, inspecting the floe’s surface and gauging the quality of the ice by jabbing it with a long rod. If the floe looked promising, a suitable area of ice was found at the bow and stern of the ship to drill 8” diameter holes for sinking 2 m long, steel pegs into the ice to secure the ship. Generally, the steel pegs were positioned about 15 to 20 m off the ship’s bow and stern, which was adequate for securing the ship. The ship was berthed so that the wind and/or ship’s propulsion system held the ship fast to the ice edge.

If the floe’s edge was too ragged to obtain a good fit between the ship and the floe, as was the case for Floe B1S2, the ship attempted to create a cleaner edge by gently clearing away some of the ice outcrops. That was not always possible, however, since the very act of swiping the ship along the edge of the floe frequently caused the edge to become more ragged. It is completely understandable, then, that the process of locating an edge where the ship could be secured to the floe, conducting an investigation of the floe surface and securing the ship took two hours, or more. It was an extremely important process because the floe needed to be stable enough to remain intact while a group of about 17 scientists (with their very expensive equipment) safely sampled the floe over a two-day period. The ice along the entire 90 m length of the ship needed to be thick and solid given that all personnel disembarked and embarked from the gangplank (towards the stern of the ship), many personnel worked immediately adjacent to the ship, and the equipment required for the NRC-CHC measurements (upwards of 500 kg) was delivered just off the bow with the ship’s crane (Figure 3). Field parties were instructed to access the floe via the ship’s gangplank only – the over-the-side basket was to be used only for transferring equipment, for safety reasons.

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Figure 3 Accessing Floe B1S2 using gangplank towards ship’s stern to provide access for personnel and forward crane to transport heavy equipment

3.2 Ice Property Measurements

The temperature and salinity of the ice were documented from cores extracted from the ice. Cores were taken in at least one borehole per floe, to a depth of 7 m where possible (the limit of the existing equipment). A gas-powered, fibreglass corer (0.15 m diameter) was used to extract the ice cores in 1 m long segments, after which the cores were processed immediately. The ice temperature was measured by inserting a digital temperature probe into holes that had been hand-drilled in the core, at 20 cm depth intervals. The time required for the temperature probe to reach equilibrium at each depth was used to cut salinity samples from the core. Semi-circular pucks, about 2 cm thick, were cut from the core at depth intervals of 20 cm. To minimize brine drainage, the salinity samples were bagged as quickly as possible, then transported to the ship, where they were double bagged to prevent leakage, and left to reach room temperature. The salinity and conductivity of the melt water were measured with an Orion model 105A portable conductivity meter.

The hydraulically activated borehole indentor, designed and fabricated at the NRC, was used to measure the in situ confined compressive strength (borehole strength) of the ice. Strength tests were performed in two 0.15 m diameter boreholes per floe, at 30 cm depth intervals, to a maximum depth of 7.0 m. The NRC borehole indentor consists of a high-strength stainless steel hydraulic cylinder with a laterally acting piston and two indentor plates, curved to match the wall of the borehole (Figure 4). A 10,000 psi electro-hydraulic pump was used to activate the indentor plates, each of which is capable of penetrating 2.5 cm into the ice, as an external digital data acquisition system recorded the displacement of each indentor plate and the oil pressure. The pressure and displacement of the indentors were also monitored with a handheld keypad to

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ensure that the 10,000 psi capacity of the system and the indentor stroke were not exceeded. Upon concluding the strength test at each depth, the indentor plates were retracted, the borehole indentor was rotated 90° (to minimize the effect of cracking on subsequent tests) and the indentor apparatus was lowered to the next depth. Note that, in this report, the ice strength is given as the maximum ice pressure attained during each strength test.

Figure 4 NRC dual acting borehole indentor

(a) two indentor plates at their full extension of 2.5 cm each and (b) borehole indentor positioned just below top ice surface, for demonstration purposes

3.3 Drill Hole Technique

Flagged transects were used to indicate where ice thickness measurements were to be made. The transects spanned both level and deformed ice in order to completely characterize the thickness of the floe. In the past, too many field programs have concentrated on level areas of multi-year ice, avoiding the more deformed areas because of the difficulties it presents. During this field program, the length and orientation of the transects were strongly influenced by where the Captain thought he might impact the floe. That made the process of mapping out transects challenging, particularly on the first day of sampling, since it was not usually known where the Captain would penetrate the floe. The technique of orienting two drill-hole transects perpendicular to the floe edge, with a third transect running between them seemed to work well (see Figure 6, for instance). The ice thicknesses were reported to the Captain upon concluding the first day’s measurements, to allow him to better decide where the impact should take place. The ship impacts occurred after the second day of on-ice measurements, when all personnel and equipment had returned to the ship.

Individual flags were distributed at 10 m intervals along each of the 80 to 200 m long transects. Once the flags had been distributed, the ice thickness and ice freeboard at each flag was measured using the so-called ‘drill-hole technique’. The drill-hole approach to measuring ice thickness is labor intensive, but it provides the most accurate means of obtaining measurements on thick multi-year ice. The technique requires using a powered drill to bore up to twenty, one-metre-long, 2”-diameter auger through the full thickness of ice. Once the bottom of the ice had been reached, the auger flights were retrieved, disconnected one by one, and the number of flights that had been used in each hole was noted as a rough measure of ice thickness. A more

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accurate thickness measurement was then obtained by lowering a weighted tape into the hole and hooking it on the underside of the ice. After the ice thickness had been measured in each hole, the ice thickness tape was slowly raised until it cleared the waterline (or residual drill cuttings in the hole). The distance from the (snow-free) top ice surface to where the tape rested at the waterline provided an indication of the ice freeboard. Once the ice thickness and freeboard had been measured along the transects, the flags were collected and each station was sprayed with water-based orange fluorescent marking paint (in preparation for the ship impact tests).

The four members of the NRC-CHC team worked together on the morning of the first day of sampling Floe B1S1. This was done as a training exercise for one of the NRC-CHC personnel – who was an Arctic neophyte – and the volunteer from University of Manitoba. By afternoon, the trainees felt competent enough to conduct their own drill-hole measurements. Two teams were formed, so that ice thickness measurements could be made at alternate flags along the same drill hole transect or along nearby transects. For safety reasons, both teams were equipped with firearms and remained within about 150 m of each other at all times. It should also be noted that the linear drill-hole transects often crossed melt ponds. The drill teams only ventured into ponds that had solid footing, and when thickness measurements could be conducted at a distance of 30 cm (or less) from the pond edge. Drilling in ponded ice has caused great difficulty in the past – in terms of both maintaining solid footing in a pond, and the number of auger lost.

3.4 Electromagnetic (EM) Induction Sensors

The ice thickness along each drill-hole transect was measured remotely with two types of electromagnetic induction sensors. University of Manitoba towed the sled-mounted electromagnetic induction “Sea Ice Sensor” (SIS) along the transects after the drill-hole measurements had been conducted and the flags collected. The orange marking paint facilitated the process, since it showed where the holes had been drilled. To the author’s knowledge, the thickness comparison between the drill-holes and the SIS system made during this field program was the first-time that the SIS system had been validated on multi-year ice more than 6 m thick, although the author has validated two other types of ground-based EM sensors on multi-year ice in excess of 10 m thick (Johnston, 2008-a).

The helicopter-based electromagnetic (HEM) system that is operated by Bedford Institute of Oceanography-Department was the other EM sensor that was used to measure ice thickness along the transects. The HEM conducted low-level passes over the drill hole transects (elevation about 10 m) and also spot-landed at each drill-hole station. Low-level flying and spot landing were both used because it provided an opportunity to examine the effect that altitude had upon the sensor’s footprint (and accuracy). As with the SIS system, this field program was the first time that this particular HEM system has been validated on multi-year ice in excess of 6 m thick. Johnston and Haas (2011) present the comparison of drill-hole results and thicknesses from the University of Alberta’s towed HEM system for very thick multi-year floes encountered in Nares Strait.

Results from neither EM system were available for incorporation into this report (K. Hochheim, I. Peterson, personal communications). Those results will be included in the report issued by the University of Manitoba in March, 2012. It is expected that the comparison of drill hole, ice-based EM, airborne EM thicknesses will be presented in that report.

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4.0 Results from Field Studies

4.1 Floe B1S1: Aug 15, 16

On 14 August, the ship arrived at Floe B1S1 (74°51.3'N, 128°17.7’W, 18:00CT). This floe was a massive fragment of a landfast hummock field (10 x 30 km) that had originated off the western coast of Prince Patrick Island (Figure 1). Satellite imagery had been used to track Floe B1S1 since early July 2011, when the massive piece of ice dislodged from coast of Prince Patrick Island, until reaching its current location 250 km south. A helicopter reconnaissance was conducted to assess the region of Floe B1S1 that would be best suited for on-ice measurements, to determine where the ship could penetrate the floe without too much difficulty, and to measure the ice thickness with the HEM system.

While the helicopter was out, the ship approached Floe B1S1 from what was mostly open water to the east (Figure 5). Skirting along the edge of the floe provided an excellent opportunity to observe that the floe had an extensive amount of recently rubbled ice and that some regions of the floe’s keel were quite porous. When the helicopter returned, the Captain was informed that Floe B1S1 was an aggregate floe of multi-year ice and deteriorated first-year/second-year ice, which the HEM indicated was about 5 m thick.

The ship continued along the south side of Floe B1S1 until it reached an area where a relatively straight transit could be made to an open water lead, roughly 1 km from the floe’s edge. The intention was to use the lead as a natural harbour for accessing the prospective sampling area that had been seen from the air. Nearly one hour of backing and ramming was required to reach that open water lead – or a total of 13 rams from 13:30CT (19:34UTC) to 14:20CT (20:20 UTC). At that point, the ship entered the lead and sailed north-west to where the lead terminated (Figure 6). The ship sidled against Floe B1S1 while the Chief Scientist and two crew members conducted their on-ice investigation. The Chief Scientist radioed back that the floe was indeed satisfactory. They then installed steel pegs to secure the ship. By 16:30CT (22:20UTC) the ship was secure.

Figure 7 shows the ship’s trajectory (before and after securing to the floe), as well as the floe’s trajectory that was obtained from NRC-CHC’s on-ice GPS2. The ship/floe combination drifted 1.8 km during the 7.2 hours spent sampling the floe on Day 1 and 2.3 km during the 6.1 hours spent sampling the floe on Day 2. Floe B1S1 drifted at an average speed of 0.25 km/hr on Day 1 and 0.38 km/hr on Day 2. Notice that the floe had a very non-linear, scalloped drift pattern, with the two most prominent cusps occurring at 21:00CT (03:00 UTC) and 09:00CT (15:00UTC). The complicated drift pattern cannot be attributed to the ship’s effect on the floe because data from sea-bottom-mounted instrumentation (Fissel et al., 2008) also have revealed highly erratic drift patterns for some floes in the Canadian Beaufort Sea.

2

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S1B1

Figure 5 Floe S1B1 as identified from satellite imagery (courtesy of Canadian Ice Service)

1 2

3

4

H1 H2

Figure 6 Aerial perspective of ship secured to Floe S1B1 in an open water lead

The approximate location of the four transects along which drill-hole thicknesses were made is shown, as is the location of the two boreholes where property measurements were made (H1, H2)

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Box 1, Site 1 start position ship/floe on Day 1 15 Aug 10:16CT (16:16UTC) start position ship/floe on Day 2 16 Aug 10:06CT (16:06UTC) end position ship/floe on Day 1 15 Aug 17:28 CT (23:28UTC) ship’s trajectory approaching floe ramming required to penetrate the floe ship trajectory

after secured to floe 14 Aug, 14:30CT (20:30UTC) end position ship/floe on Day 2 16 Aug (22:13UTC) 16:13CT

Figure 7 Trajectories of the ship and Floe B1S1 from 14 to 16 August

Start and end times of Day 1 and Day 2 correspond to time spent on the ice; blue markers show the trajectory obtained from the GPS used by the ice floe party during Day 2

Floe B1S1 was sampled for two days. The morning of Day 1 was used to conduct drill-hole measurements along Transect 1 (90 m long, see Figure 6); the afternoon was spent conducting property measurements in a level area of ice along Transect 1, between Flags BB2 and BB3 (Figure 8-a, Figure 9-a). Ice cores were extracted from one borehole to measure the temperature and salinity of the ice, and a complete set of strength tests was conducted in two boreholes. Although the boreholes were made in a very level area of ice, the surface topography of the floe in other areas was more dramatic (see Figure 8-b). It was not possible to man-haul the two very heavy sleds of equipment to heavier terrain, however3.

The second day of on-ice sampling was used to measure the ice thickness along Transects 2, 3 and 4. These three transects had been mapped towards the stern of the ship because that morning the Captain mentioned that was where he intended to impact Floe B1S1. Based upon that information, the NRC-CHC teams mapped two transects perpendicular to the floe edge and the third transect parallel to the floe edge, as shown in Figure 6.

3

A snow machine had been rented specifically for hauling NRC-CHC equipment over hummocked multi-year ice, but the snow machine had not yet been removed from its shipping location (on top of one of the cargo modules).

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Figure 8 Floe B1S1: (a) region where strength tests were conducted in two boreholes along Transect 1 and (b) surface topography along one of the drill hole transects, with helicopter-borne

EM survey being flown in distance

(a)

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4.1.1 Surface and bottom topography along drill hole transects

The NRC-CHC team measured the ice thickness at 49 drill holes along four transects over the two-day sampling period. The ice thickness ranged from 3.6 to 9.3 m at the individual drill holes. Most of the drill holes were from 6 to 7 m thick, however, which is why Table 2 shows comparable average thicknesses for the different transects (6.3 to 7.7 m, with standard deviations from 0.6 to 1.5 m). Transect 1 had the least inter-hole variability in thickness (±0.6 m) whereas Transect 3 had the greatest variability in thickness (±1.5 m). Figure 9 shows the plan view of the Floe B1S1 along the four drill-hole transects, in terms of the ice freeboard and the ice draft. The ice freeboard at the individual holes ranged from 0.0 m (edge of a pond, where the surface of the ice was depressed to the waterline) to 2.0 m (hummock), resulting in an average freeboard of 0.7 m for the 49 holes. Notice that the ice along the two transects that were oriented perpendicular to the edge of the floe (transects 2 and 4) did not show evidence of thinning as the open water lead was approached. That may have been because the lead was inside the floe, rather than being on the leading edge of the floe.

Table 2 Summary of ice thicknesses measured on Floe B1S1

No. of drill holes Length of transect (m) Average thickness (m) Maximum thickness (m) Minimum thickness (m) Transect 1 10 90 7.5 ± 0.6 8.5 6.9 Transect 2 9 80 7.7 ± 1.2 9.3 5.8 Transect 3 9 80 6.3 ± 1.5 7.6 3.6 Transect 4 19 190 7.1 ± 1.3 8.9 4.8 Floe B1S1 49 7.2 ± 1.4 9.3 3.6

4.1.2 Temperature, salinity and strength of Floe B1S1

The strength of the Floe B1S1 was measured in two boreholes. Ice cores were extracted from one of the boreholes (H1, 7.2 m thick) to document the temperature and salinity of the ice; the other borehole (H2, 7.3 m thick) was merely augered to produce a hole in which to measure the strength of the ice. Both H1 and H2 were made in a level area along Transect 1 (between Flags BB2 and BB3, Figure 8-a), where the ice was 7 m thick, as shown in Figure 9-a.

Coring at H1 was an interesting experience. The uppermost three metres of ice in H1 produced a solid core that, although warm and saturated, had some integrity. Below the 3 m depth, a very slushy mixture, intermixed with a few larger fragments of ice, was all that could be captured. The photographs in Figure 10 show the cores extracted from two different depths: (a) the top 0.60 m of ice and (b) from depths of 2.7 to 3.0 m. Note that the uppermost 0.20 m of ice was white, soft and slushy – it could have easily been mistaken for snow ice. The core itself confirmed the kind of transformation that the top surface of the floe underwent throughout the day: as the day progressed, the ice deteriorated and became more granular, which made walking and hauling gear over the surface much more difficult.

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BB10 BB9 BB8 BB7 BB6 BB5 BB4 BB3 BB2 BB1 -12 -8 -4 0 4 -20 0 20 40 60 80 100 th ic kn e ss ( m ) Transect 1 O2 O3 O4 O5 O6 O7 O8 O9 O10 -12 -8 -4 0 4 -20 0 20 40 60 80 100 th ic k nes s ( m ) Transect 2 O12 O13 O11 O14 O15 O16 O17 O18 O19 O20 -12 -8 -4 0 4 -220 -200 -180 -160 -140 -120 -100 th ic kn e ss ( m ) Transect 3 B20 B19 B18 B17 B16 B15 B14 B13 B12 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 -12 -8 -4 0 4 -40 -20 0 20 40 60 80 100 120 140 160 180

distance along drill-hole transect (m)

th ic k nes s (m ) Transect 4

Figure 9 Profile view of Floe B1S1: topography of top ice surface and bottom ice surface along drill-hole transects

(a)

(b)

(c)

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The holes that had been drilled along Transect 1 earlier that day revealed soft ice that presented little resistance to drilling. Voids had been encountered in many of the 2” diameter holes, beginning at an ice depth of 2.2 m and occurring intermittently until reaching the bottom of the floe. However, it should be noted that the 3 m long core from H1 did not contain voids (as the photographs in Figure 10 illustrate) nor were voids felt at that location when drilling a 2” hole for thickness measurements.

Temperature: Since ice temperature measurements depend upon the amount of solid core that

can be extracted from the ice, the temperature profile of H1 was limited to the uppermost 3 m of ice. Results showed that the temperature of the top ice surface was +0.2°C and gradually decreased to a minimum of -1.7°C at the 3 m depth (Figure 11-a). The average temperature of the uppermost 3 m of ice was -0.9°C.

Salinity: The salinity profile also depends upon the amount of core that is able to be extracted

from the ice, but salinity samples can be obtained from even slushy ice (which are melted). Slushy samples can be used, but it is impossible to determine to which depth they correspond. That is why the salinity profile in Figure 11-b extends to the 3.8 m depth, rather than terminating at the 3 m depth, as did the temperature profile. The salinity of Floe B1S1 ranged from 0‰ to 3.1‰, with an average salinity of 1.8‰. Note that the low salinity layer of ice extended to only the 0.2 m depth, which was only part way through the 0.6 m freeboard at H1. It is also interesting to note that the ice salinity was quite high considering that Floe B1S1 originated from a landfast hummock field. Traditionally, landfast multi-year hummock fields are expected to be quite old, therefore would have a thick surface layer of low salinity ice.

Strength: Results from the borehole strength tests speak volumes about the quality of ice

comprising Floe B1S1. Although the ice at boreholes H1 and H2 was 7 m thick, only the uppermost several metres had ‘respectable’ strength (Figure 11-c). Here, ‘respectable’ is loosely defined as a peak borehole ice pressure of 5 MPa, or more. Strengths in the uppermost three metres of ice from Floe B1S1 ranged 7.3 to 15.6 MPa. In comparison, only three of the strength tests conducted in the bottom 4 m had peak ice pressures marginally higher than 5 MPa (the 5.1 and 5.4 m depths in H1, and 4.8 m depth in H2). To provide a frame of reference, Johnston and Timco (2008-b) showed that first-year ice at a latitude of 74°N had a peak borehole ice pressure of about 9 MPa in early July. In comparison, the average strength of the 7 m thick ice at the two boreholes on Floe B1S1 was 7.3 MPa and 4.5 MPa.

It should be noted that the strengths reported here were obtained from the maximum pressure attained at each test depth. In several cases, however, the maximum ice strength at a particular depth would actually be higher than the maximum pressure recorded during a test because the pressure continued to rise (albeit slowly) until the indentors were retracted after reaching their full 25 mm of travel.

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Figure 10 Cores from borehole #1 (a) uppermost 0.6 m of ice and (b) depths 2.7 to 3.0 m ice cores are oriented top (left) to bottom (right)

(a)

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Max ice pressure (MPa) -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 0 5 10 15 20 Hole 2 Hole 1 Hole 1 = 7.2 m Hole 2 = 7.3 m -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 0 1 2 3 4 Ice salinity (‰) H1 = 7.2 m thick Hole 1 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 -2 -1 0 1 2 Ice temperature (C) Ice dep th ( m ) H1 = 7.2 m thick Hole 1

Figure 11 Temperature, salinity and strength profiles of Floe B1S1

4.1.3 Ship impact tests with Floe B1S1

The ship penetration tests took place on 16 August, after concluding the on-ice measurement portion of the floe study. A total of ten controlled impacts were conducted from 19:30 to 20:20CT (01:30 to 02:20UTC). The Captain aimed for an area of ice between Transects 2 and 4 during the ten controlled impacts on 16 August. Fluorescent marking paint had been used to facilitate the aiming process, but even so, it was still very difficult to see the marked drill-hole transects from the bridge when approaching the floe from a distance. The aiming process was also complicated by the fact that the ship’s approach distance was severely restricted during the first few rams – since the open water lead was quite narrow, the ship didn’t have far to travel before it encountered multi-year ice in front, and behind. To the Captain’s credit, his aim was perfect: the first impact occurred just to the right of Transect 4.

Figure 12 shows the ship’s trajectory during the 10 controlled impacts. The tests were conducted at approach speeds of 2.5 to 8.8 kt, which covered the widest possible range of speeds still within the Captain’s comfort level. An approach speed of 2.5 kt was used for the first ram, after which the impact speed was gradually increased to a maximum of 8.8 kt (for the tenth ram). The photographs in Figure 13 show the bow print caused by the first ram, compared to the bow print from the tenth ram. By the sixth ram, the ship had penetrated the floe up to Transect 3, which was roughly 110 m from the floe edge. By the tenth ram, the ship had penetrated the floe by

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about two to three ship lengths. The global ice impact forces for each of the rams will be presented in a separate report (Johnston, in preparation).

Recall that a total of 13 impacts were also conducted with Floe B1S1 in order to reach the open water lead on 14 August. The rams on the 14 August were useful certainly, but they lacked supporting information about the thickness and strength of the ice. That information was available for the ten controlled impacts that were conducted on 16 August. It will be useful to compare global forces from impacts conducted with the different regions of the floe, on the different days, since the results would be expected to be similar.

Floe B1S1 Ram #1 #10 #8 #9 #7 #6 #5 #3 #4 #2

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Figure 13 Bow prints caused by (a) first ram and (b) last ram with Floe B1S1

Ram #1 was conducted at 2.5 kt and Ram #10 was conducted at 8.8 kt

(a)

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4.2 Floe B1S2: Aug 17 – 18

After concluding operations on Floe B1S1, the ship traveled 33 km northwest in search of another deformed multi-year ice floe on which to make measurements. Several targets were explored until the hummocked area of ice called Floe B1S2 at 09:00CT (15:00UTC) was settled upon. The hummocked area (200 m by 400 m) was embedded in a multi-year ice floe that satellite imagery showed was roughly 6.5 by 6.5 km (Figure 14). The ice chart indicated that Floe B1S2 was situated in a region of 6/10ths old ice (Figure 1) and 1/10th thick first-year ice or 7/10ths total ice concentration.

S1B2

Figure 14 Floe S1B2 as identified from satellite imagery

(courtesy of Canadian Ice Service)

By 09:15CT (15:15UTC) the Chief Scientist and several crew members had been deployed for an on-ice investigation. Having determined the ice to be satisfactory, a location was sought for securing the ship. The ragged edge of the floe made this quite challenging. The Captain proceeded to clean the floe edge to produce an area to secure the ship. By 10:15CT, the ship had been secured to steel pegs off the ship’s bow and stern, as shown by the aerial photograph in Figure 15.

Over the two days that were spent sampling Floe B1S2, the ship/floe combination drifted 1.2 km during the 4.7 hours spent on the ice the first day, and 2.1 km during the 7.8 hours spent on the ice the second day. The average drift rate of the floe was 0.25 km/hr on Day 1 and 0.27 km/hr on Day 2, as noted in Table 1. Floe B1S2 maintained an undulating drift pattern over those two days (Figure 16), but its trajectory was considerably more uniform than Floe B1S1’s trajectory had been (Figure 7).

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1

2

3 H1 H2

Figure 15 Aerial perspective of ship secured against Floe S1B2

The approximate location of the four transects along which drill-hole thicknesses were made is also shown (photo courtesy of S. Prinsenberg)

Box 1, Site 2 start position

ship/floe on Day 1 17 Aug 13:26CT (19:26UTC) start position ship/floe on Day 2 18 Aug 9:07CT (15:07UTC) end position ship/floe on Day 1 17 Aug 18:28 CT (00:09UTC) end position ship/floe on Day 2 18 Aug (22:55UTC) 16:55CT

Figure 16 Trajectories of Floe B1S2 (and the ship) during two days of on-ice measurements

Start and end times of Day 1 and Day 2 correspond to time spent on the ice; green markers show the trajectory obtained from the GPS used by the ice floe party for the two days of sampling

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On-ice operations commenced on Floe B1S2 after lunch on 17 August (13:30CT) and continued until 17:15CT (23:15 UTC). Three drill-hole transects were mapped out on the floe, as shown in Figure 15. Thirty of the drill holes were completed on Day 1, leaving the remaining ten to be completed on Day 2. On Day 1, thickness measurements were made at the flags furthest from the ship. That left only the flags nearest the ship to be completed on Day 2 (should poor weather restrict visibility). Ice property measurements focused upon the largest hummock in the sampling area. Figure 15 shows the location of the first borehole (H1) in which only strength tests were conducted, and the second borehole (H2) where the temperature, salinity and strength of the ice were measured. The on-ice photographs in Figure 17 show (a) Transect 1 extending perpendicular to the floe edge off the ship’s bow and (b) the hummock on which borehole strength tests were conducted.

4.2.1 Surface and bottom topography of Floe B1S2

Table 3 summarizes the ice thicknesses measured along each of the three transects. Transect 1 was 190 m long, Transects 2 and 3 were each 90 m long. The thickness of ice measured at the different drill holes ranged from 5.1 to 15.7 m. The average thickness along the three transects was quite similar (8.3, 8.0 and 7.3 m) despite thicknesses being much more variable along two of the transects, than the third. Standard deviations for Transects 1, 2 and 3 were respectively ±2.4, ±3.0 ±1.5 m. The freeboard of Floe B1S2 at the 40 drill holes ranged from 0.2 m to 2.3 m, for an average freeboard of 0.9 m. The surface and bottom topography profiles in Figure 18 illustrate the kind of variability that occurred along the different transects. Note that Transect 2 did not cross the 2.7 m high hummocked feature on which ice property measurements were made. The properties of that hummocked feature are discussed below.

The drilling experience on Floe B1S2 was quite different than it had been on Floe S1B1. The drill holes indicated that the ice ranged from medium to hard, with variations in adjacent holes and often within the same hole. Several of the drill holes on Floe B1S2 had soft ice towards the bottom of the ice sheet, however voids were noticeably absent from most of the drill holes.

4.2.2 Temperature, salinity and strength of Floe B1S2

The strength of the most prominent hummock in the sampling area was measured in two boreholes. Figure 17-b shows the area of ice in which the first borehole (H1) was made. That borehole was merely augered to produce a hole for strength measurements. The ice at H1 was 14.3 m thick and had a freeboard of 2.7 m. A second borehole was made about 10 m further along the crest of the hummock (H2). Although the thickness and freeboard of H2 were not measured due to time constraints, cores were extracted to a depth of 7 m in H2.

The cores from Floe B1S2 revealed competent, solid ice to a depth of 7 m – which was very different than had been the case on the previous floe, Floe B1S1. That stands to reason, because the surface of Floe B1S2 certainly had more hummocks, those hummocks were more weathered (smoothed) and the floe surface was not a deteriorated as Floe B1S1.

Temperature: The temperature of the uppermost metre of ice at H2 was near isothermal at 0°C,

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relatively uniform from depths 5.2 to 6.4 m, then gradually warmed to -3.7°C at the 7 m depth. The average temperature of the uppermost 7 m of ice was -2.6°C.

The ice temperature profile for Floe B1S2 was somewhat erratic because problems were encountered retrieving the core itself. Many times, fragmented pieces of cores were unable to be retrieved with the core barrel. A considerable amount of time (and patience) was needed to retrieve the remnant pieces from the borehole with a fishing tool. Still, it was impossible to retrieve all of the pieces, and many of the fragments were too small to measure the ice temperature. As a result, temperature measurements are not available for two depths ranges (from 3.9 to 4.2 m; from 5.4 to 6.2 m). The considerable time that was spent recovering individual core fragments sometimes altered their temperature, particularly if the fragment was lodged in a water-filled borehole. By late-summer, water typically creeps into the borehole before the full thickness of ice has been penetrated.

Salinity: The salinity of H2 ranged from 0.1 to 2.1‰ within the uppermost 7 m of ice, for an

average salinity of 1.0‰. The salinity profile in Figure 19-b is characterized by three relatively distinct regions: (1) the uppermost 2.0 m of ice where salinities were less than 0.2‰, (2) the region from depths 2.0 to 3.6 m where the salinity increased from 0.1 ‰ to 1.8 ‰ and (3) depths 3.6 to 7.0 m where most of the salinities were close to 1.8‰. It is noteworthy that, although the hummock had a freeboard of 2.7 m, the lowest salinity layer characterized only the uppermost two metres of ice – the low salinity layer does not necessarily correspond to the ice freeboard, which has sometimes been suggested.

Strength: A full set of strength tests were conducted in H1 but, due to time constraints, only

depths 4.2 to 6.6 m were tested in H2. Realizing that time was limited, it was decided to conduct strength tests in H2 from the bottom to the top, in order to capture the coldest, strongest ice first. Tests showed that the hummocked feature had very respectable strengths at all depths, ranging from a minimum of 11.1 MPa to a maximum of 30.8 MPa (Figure 19-c). The average strength of the uppermost 7 m of the hummock was 22.0 MPa. These strengths represent the maximum pressure attained at each test depth. The peak pressure for all of the strength tests in each borehole occurred before the maximum indentor travel had been reached.

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Figure 17 Floe B1S2: (a) drill-hole Transect 1 extending perpendicular to ship and (b) the 14.3 m thick hummock on which temperature, salinity and strength measurements were made

(a)

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Table 3 Summary of ice thicknesses measured on Floe B1S2 No. of drill holes Length of transect (m) Average thickness (m) Maximum thickness (m) Minimum thickness (m) Transect 1 20 190 8.3 ± 2.4 14.8 5.1 Transect 2 10 90 8.0 ± 3.0 15.7 5.3 Transect 3 10 90 7.3 ± 1.5 9.9 5.7 Floe B1S1 40 8.0 ± 2.3 15.7 5.1 O20 O19 O18 O17 O16 O15 O14 O13 O12 O10 O11 O9 O8 O7 O6 O5 O4 O3 O2 O1 -16 -12 -8 -4 0 4 -20 0 20 40 60 80 100 120 140 160 180 200 220 th ickn e ss ( m ) 0.36 O2 O3 O4 O5 O6 O7 O8 O9 O10 -16 -12 -8 -4 0 4 -120 -100 -80 -60 -40 -20 0 th ickn e s s ( m )

O20 O19 O18 O17 O16 O15 O14 O11 O13 O12

-16 -12 -8 -4 0 4 -20 0 20 40 60 80 100

distance along drill-hole transect (m)

th ickn e ss ( m ) Transect 3

Figure 18 Floe B1S2: Profile view of surface and bottom topography along drill-hole transects

(a)

(b)

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Max ice pressure (MPa) -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 0 5 10 15 20 25 30 35 Hole 2 Hole 1 Hole 1 = 14.2 m Hole 2 = ? m -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 0 1 2 3 Ice salinity (‰) Hole 2 H2 = ? m thick -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 -6 -4 -2 0 2 Ice temperature (C) Ice dep th ( m ) H2 = ? m thick Hole 2

Figure 19 Temperature, salinity and strength profiles of Floe B1S2

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4.2.3 Ship impact tests with Floe B1S2

By 17:00CT (23:00UTC), the on-ice measurements had been concluded and all personnel and equipment had returned to the ship. At 20:00CT, the ship made ready for impacting Floe S1B2. Realizing that Floe B1S2 was not at all like Floe B1S1, the Captain planned to impact the floe very gently at first, and to limit the number of rams that were conducted.

A total of four controlled rams were conducted with Floe B1S1 from 20:20CT to 20:40CT. The first ram took place at a speed of 2.5 kt, as the ship impacted the floe about 30 m to the left of Transect 1. A deep, hard hit was felt on the bridge, yet the ship left but a small imprint in the floe edge (Figure 21-a). The second ram occurred at a ship speed of 3.3 kt, leaving a slightly bigger impression in the same notch created by the first ram. The third ram took place at a speed of 5 kt and although it too involved the same notched area, the resulting hit was quite a bit more substantial than the previous two rams. The fourth and final ram was conducted at a speed of about 7 kt. The last impact caused significant ride-up; it also generated a large crack that propagated through a nearby melt pond (Figure 21-b). The fracture following an interconnected drainage feature to the edge of the floe, effectively severing a large chunk of ice from the floe.

Floe B1S2

Impact #1 #2

#3 #4

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Figure 21 Bow prints caused by (a) first ram and (b) last ram with Floe B1S1

Ram #1 was conducted at 2.5 kt and Ram #4 was conducted at 7.0 kt

(a)

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5.0 Conclusions

5.1 Multi-year ice thickness by direct drilling

Ice thicknesses were measured on two multi-year ice floes in the Beaufort Sea. The average thickness of the two floes was 7.2 ± 1.4 m and 8.0 ± 2.3 m, which is comparable to the average thickness and standard deviations that have been measured in other parts of the Arctic (Figure 22). The average thickness of the multi-year floes on which the author has conducted drill-hole measurements over the past five years has ranged from 3.4 to 14.7 m (±0.7 to 4.3 m). The median average thickness of the 28 floes was 7.5 m. The two floes with the greatest average thickness (12.7 m and 14.7 m) were both sampled in Sverdrup Basin, which suggests that a greater proportion of floes in that area are deformed, compared to elsewhere in the Arctic.

7.2 8.0 6.2 9.2 14.7 12.7 10.2 6.5 4.7 8.3 8.6 3.4 4.2 8.1 9.3 8.6 7.3 3.6 9.6 + 7.7 + 8.7 + 5.1 9.5 + 5.1 4.9 5.9 4.8 8.8 + 0 2 4 6 8 10 12 14 16 18 20 N0 1 N0 2 N0 3 N0 4 N0 5 N0 6 N0 7 N0 8 N0 9 N1 0 N1 1 R0 1 R0 2 R0 5 LC I0 1 L01 L02 L03 L04 L05 L06 L07 L08 L09 L08 W0 1 B1 S1 B1 S2

Sampled multi-year ice floe

A v er ag e d ri ll-ho le i c e t hi c k n es s ( m High Arctic (2007) Resolute (2008) High Arctic (2009) Resolute (2010) Beaufort (2011)

Figure 22 Comparison of five years of drill hole measurements on multi-year floes

Average thicknesses with a “+” indicate floes that the bottom of the ice was not reached in some holes, producing a lower bound for the average thickness.

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5.2 Temperature, Salinity and Strength of Sampled Floes

Only two multi-year floes were able to be sampled during the two week voyage on the CCGS

Amundsen but, interestingly enough, those two floes provided about a wide spectrum of multi-year ice. Floe B1S1 (74.8°N, 128.3W) was at one end of the spectrum. Although it had originated from the landfast multi-year hummock field off the coast of Prince Patrick Island, it was quite warm, saline and relatively weak. Only the uppermost three metres of the 7 m thick level ice had respectable strength. The remainder of the ice had strengths of 5 MPa or less – which is less than the strength of first-year ice (at 74°N) in early July (9 MPa). The average strength of the 7 m thick ice from two boreholes was 7.3 MPa and 4.5 MPa. Floe B1S1 would have posed a hazard to ships with limited ice strengthening, but it presented little difficulty for the CCGS Amundsen (8500 t). A total of 10 controlled impacts were conducted with Floe B1S1, by which time the ship had penetrated several lengths into the floe.

Floe B1S2 (75.0°N, 129.0°W) was at the other end of the spectrum. The hummocked feature that was tested on Floe B1S2 was thicker, colder and less saline than ice tested in the previous floe. It was also considerably stronger: all test depths in the uppermost 7 m of ice had very respectable strengths. The average strength of the uppermost 7 m of the hummock was 22.0 MPa. It is not surprising then, that the CCGS Amundsen responded very differently to impacts with Floe B1S2. The first three rams produced only a small imprint in the floe edge; only after the fourth and final ram did a crack propagate through the floe, by exploiting local weaknesses in the ice (a ponded area and its adjacent drainage feature).

Max ice pressure (MPa)

-8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 0 5 10 15 20 25 30 S1B1 S1B2 S1B1 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 0 1 2 3 4 Ice salinity (‰) S1B1 S1B2 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 -6 -4 -2 0 2 Ice temperature (C) Ice dept h ( m ) S1B1 S1B2

Figure 23 Properties of two very different floes sampled during the voyage: Floe B1S1 and Floe B1S2

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6.0 Recommendations for future Beaufort Sea Field Programs

At the request of one of the project sponsors, the author includes here some suggestions about what would be useful for future field programs on multi-year ice in the Beaufort Sea, in similar conditions. These recommendations are based upon more than 10 years experience sampling Arctic multi-year ice from icebreakers such as the CCGS Louis S. St-Laurent (Oct. 2003, Oct. 2005), CCGS Henry Larsen (Aug. 2006, Aug. 2007, Aug. 2009) and most recently from the CCGS Amundsen (Aug. 2011).

In the past, the helicopter was a vital means of transporting personnel and gear to multi-year floes. Most of the sampled floes were in close proximity to the ship (less than 10 km), although several were considerably further a field. The helicopter is the most efficient means of transporting the field party of four, and their approximately 600 kg of equipment, to the interior of ice floes. For this project, the author was keenly interested in witnessing the practice of tying the ship to a floe and then using the gangplank to access the floe. From this experience, it was concluded that the practice could be used to safely conduct on-ice measurements within several hundred metres of the floe edge, provided the floe is sufficiently massive (didn’t fracture upon impact) and that sound judgment, experience and care are taken to evaluate the condition of the floe edge before personnel and equipment are put on the ice. Ultimately, it is the Commanding Officer that decides whether the floe is competent and where the ice can be safely sampled.

If the ship is used to tie up to the floe, measurements will be biased towards the more massive ice features. Many floes were considered inferior because they split upon impact, yet would have been perfectly satisfactory for conducting on-ice measurements, had a helicopter been used for floe access. Since the objective of this program was to sample potentially unmanageable ice features, that was not a serious limitation. However, it would bear upon the success of field programs seeking to sample a wider spectrum of ice.

If the intention is to sample ice towards the interior of the floe, rather than at the floe edge, as was done in this program, a helicopter would be needed. Using a snow machine to access the interior of the floe is not recommended – first, because the weather can change rapidly; second, because melt ponds and thin ice are both hazardous on late-season multi-year ice.

In the author’s mind, the helicopter is preferred mode of accessing the ice. It allows features of interest to be identified, can be used to efficiently transport people to the area of interest (to maximize time on the ice), permits low-level aerial photographs of the sampling area to be taken, and is an excellent means of measuring the floe size. The helicopter is weather-limited, but it can, and has been used to safely access ice within several hundred metres of the ship even in moderately foggy conditions, when the Captain and pilot permit.

Other recommendations:

• at least two to three metres of small diameter ice auger should be taken to quickly drill a few holes to measure the thickness and quality of the ice before allowing personnel onto the ice

• the ship’s crane should have greater reach, in order to permit heavy equipment to be delivered well away from the floe edge

• all personnel on the ice and on the bridge should remain vigilant about any and all cracks developing on the ice surface

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• having sufficient radio communication while working on the ice is paramount: groups need to be able to communicate to the bridge, but also to one another

• each group should have a dedicated wildlife monitor when not working in close proximity (200 m or less in clear weather) to each another

• communication between the author and the deck crew was problematic, at times, particularly when delivering large amounts of equipment to the floe. Both of the author’s technicians were bilingual, but requiring an intermediary is not the most efficient means of communicating and, in certain situations, time may not permit that exchange to take place. It is recognized that this would not have been an issue had the author been bilingual. It is mentioned here only to underscore the importance of clear communication.

• in the future, it would be preferable to make low level flights with the helicopter after all field parties have left the floe. Spot-landing at the ice thickness stations made it difficult to hear/communicate during the strength tests. The debris created by the propeller wash could have easily damaged expensive equipment.

7.0 Acknowledgments

This Joint Industry Project (JIP) was made possible through the financial support of Imperial Oil Resources Ventures Ltd and University of Manitoba. B. Maddock and D. Matskevitch, from ExxonMobil, were instrumental in laying the groundwork for CHC-NRC’s participation in this program and for providing their comments on the report. The support of Officers and Crew of the Canadian Coast Guard icebreaker CCGS Amundsen is appreciated, as is the support from D. Barber of the University of Manitoba. Special thanks go to D. Barber who, as Chief Scientist, kindly provided a dedicated person for the NRC-CHC measurements, even though University of Manitoba’s full science agenda could have made use of that extra person. R. Lanthier, Y. Brunet and J. Barber deserve much of the credit for the project’s success because they helped conduct the on-ice measurements. K. Lucas gratefully provided wildlife assistance for the NRC-CHC party during the measurement program. The ongoing support of the National Research Council’s Design and Fabrication Services (DFS) is sincerely appreciated since they provide customized equipment needed to tackle multi-year ice.

8.0 References

Brovin, A. and I. Turnbull (2011) Daily Observation Report for 14 August 2011, CANATEC Associates International, Ltd. 5 p.

Barber, D. G., R. Galley, M. G. Asplin, R. De Abreu, K.-A. Warner, M. Pucko, M. Gupta, S. Prinsenberg, and S. Julien (2009) Perennial pack ice in the southern Beaufort Sea was not as it appeared in the summer of 2009, Geophys. Res. Lett., 36, L24501, doi:10.1029/2009GL041434, 5 p.

Fissel DB, Marko JR, and Melling H (2008). "Advances in Marine Ice Profiling for Oil and Gas Applications," Proceedings IceTech '06 Conference, July 20-23, Banff, Alberta, Canada.

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Johnston, M. (2008-a) Characterizing Multi-year Ice Floes in the High Arctic: Evaluating Two, Ground-based EM Sensors. Controlled Technical Report CHC-CTR-073. National Research Council Canadian Hydraulics Centre, Ottawa, Canada, March 2008, 70 p. plus appendices

Johnston, M. and C. Haas (2011) Validating Helicopter-based EM (HEM) Thicknesses over Very Thick Multi-year Ice. Proceedings 21st International Conference on Port and Ocean Engineering under Arctic Conditions, POAC’11, 10 to 14 July 2011, Montreal, Canada, paper POAC11-32, 11 p.

Johnston, M. and G. Timco (2008-b) Understanding and Identifying Old Ice in Summer. Technical report CHC-TR-055, December 2008, Ottawa, 236 p.

Johnston, M., Masterson, D. and B. Wright (2009) Thickness of Multi-year Ice: Knowns and Unknowns, Proceedings 20th International Conference on Port and Ocean Engineering under Arctic Conditions, Paper POAC09-120, Luleå, Sweden, 13 p.

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BB1 BB2 BB3 BB4 BB5 BB6 BB7 BB8 BB9 BB1 0 O10 O9 O8 O7 O6 O5 O4 O3 O2 O12 O13 O11 O14 O15 O16 O17 O18 O19 O20 B11 B10B9 B8 B7 B6 B5 B4 B3 B2 B1 B12 B13 B14 B15 B16 B17 B18 B19 B20 -100 -50 0 50 100 150 200 250 -250 -200 -150 -100 -50 0 50 100 X distance (m) Y dista n ce (m) Transect 1 Transect 2 Transect 3 Transect 4 Floe B1S1 O20 O19 O18 O17 O16 O15 O14 O13 O12 O10 O11 O9 O8 O7 O6 O5 O4 O3 O2 O1 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B20 B19 B18 B17 B16 B15 B14 B13 B12 B11 -50 0 50 100 150 200 -150 -100 -50 0 50 100 X distance (m) Y di s tanc e ( m ) Transect 1 Transect 2 Transect 3 Floe B1 Site 2

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10 Aug, Wed:

Arrive at airport at 08:00 to meet Yvan and Richard at airport to take 9:50 direct flight to Quebec. Arrive in Quebec at 11:00. Check into hotel near airport.

11 Aug, Thurs:

Meet in hotel lobby at 04:15 a.m. Take taxi to Trans Sol Aviation at Quebec airport. Arrive at 04:30, already people are waiting outside the door of the building. Check our bags, which were individually weighed to ensure they do not go over 20 kg limit. Wait for plane until 06:00. Board First Air charter to Kugluktuk; routed through Iqaluit and then Rankin Inlet (the weather there was poor in the morning, so we were diverted to Iqaluit, meanwhile the weather improved). The flight was supposed to arrive at 09:30 Mountain time (11:30 EST) but we didn’t arrive until (12:30) 2:30 EST. Then the crew change took place, step by step. Waited in airport until at least 15:30, when I was taken aboard, along with Simon, Megan and Dustin. Saw the logistics officer, signed forms, went to room and unpacked personal gear. No sign of baggage or box that was shipped individually to Quebec. Went to bridge to check on event trigger box, green light on. Luggage delivered at 19:30. Unpack personal gear. Sharing room with Lucie (environmental advisor). She arrived on a flight this morning with about 15 other people from ExxonMobil, Imperial, Canatec, Ron Ritch. Meeting of all scientific personnel at 20:00 hours (ship is currently on Quebec time, due to switch to Central time later this evening).

To do:

• check MOTAN DAS to see if green light is on (acoustic well room, 6th

deck). • post dangerous goods contents on paleo lab door

• locate and unpack equipment

• obtain gas for motor heads/generator

• locate grey drum with hardhats (sent to Quebec, on its own prior to departing)

12 Aug. Friday

Transit to sampling area in Box 1. Open water most of the way. Get equipment from Cargo #2 (partly by Richard and Yvan taking it down the ladder, and partly by CCG using jib crane to remove it). Unpack equipment. Obtain gas. Obtain chemicals. Post sign about chemicals. Have meeting about science – who does what and safety protocols for each project.

13 Aug. Saturday

Wake in morning to see ice outside window. Still making way towards Box 1. Spot several polar bears in morning. Spend entire day looking for floes large enough for all of Dave’s group to work on; and floes that hold together as ship sidled against them. Captain Thibault tells me that he spoke to Captain Julien last night, and he now has a clearer picture of what is needed for MOTAN. He offers to impact several floes en route to Box 1; is quite keen to do it. Asks if I would like the ship’s camera to take pictures. I decline. The day is filled with impacts for MOTAN – both from Captain Thibault impacting several floes of choice, plus impacts from trying to attach ourselves to a floe for sampling (50 plus hits). At 4:07 he prepares for first impact. Event #1 is an ice piece with sails up to approx. 5 m high. The ship drives into the floe symmetrically, pushes the floe, it cracks around the ship. He reverses about one ship length, then prepares to impact it at 2 kt and says that he won’t get through it. The impact turns out to be more like 3 kt, the floe does not break, rather the ship pushes the floe as radial cracks form around it. No real impact to speak of. Event #2 occurs when the ship impacts a piece of ice on

Figure

Figure 1  Location of sampled multi-year ice floes and “Box 1”, the initially selected study area   Map shows only the old ice concentration for 15 August, based upon CIS Regional Ice Chart
Table 1  Multi-year floes sampled during Leg 2A
Figure 2  Voyage of the CCGS Amundsen during Leg 2A    (a) from 11 to 20 August and (b) from 22 to 25 August
Figure 3  Accessing Floe B1S2 using gangplank towards ship’s stern to provide access for  personnel and forward crane to transport heavy equipment
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