Monitoring global ice impact forces on the CCGS Louis S. St-Laurent : interim report

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Monitoring global ice impact forces on the CCGS Louis S. St-Laurent : interim report

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Monitoring Global Ice Impact Forces on the

CCGS

Louis S. St-Laurent: Interim Report

M. Johnston

Technical Report, CHC-TR-086

March 2012

0 5 10 15 20 25 30

09 Jul 13 Jul 17 Jul 21 Jul 25 Jul 29 Jul 02 Aug 06 Aug

Day/Month on which ship ram occurred

Gl oba l i m pa c t f o rc e ( M N ) Peel/Victoria in 2008 (n = 166) Peel Victoria in 2009 (n = 10) Peel/Victoria in 2010 (n = 16)

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Monitoring Global Ice Impact Forces on the

CCGS

Louis S. St-Laurent: Interim Report

M. Johnston

Canadian Hydraulics Centre National Research Council of Canada

Montreal Road Ottawa, Ontario K1A 0R6

FINAL REPORT prepared for: Transport Canada Ottawa, Ontario Technical Report, CHC-TR-086 March 2012

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An inertial measurement system called MOTAN is used to measure global ice impact forces on the CCGS Louis S. St-Laurent (LSSL) during its past three voyages to the Arctic. More than 850 single rams and repeated rams with ice floes are considered here, but the thousands of additional ‘transient’ impacts that occur each season are not presented. The ramming activity was categorized into six Arctic Regions. A total of 439 rams were conducted during the 2008 season, compared to 280 rams during the 2009 season and 160 rams during the 2010 season. The least amount of ramming activity occurred in Region 1 (Baffin Bay/Lancaster Sound) and Region 3 (Coronation Gulf), whereas the greatest number of rams occurred in Region 2 (Peel Sound/Victoria Strait) and Region 6 (QEI/Banks Isl). The amount of ramming activity seemed not to be related to the magnitude of the global forces for the different Regions.

The average ram-related global force was 10.5MN ± 3.4MN for the 2008 season (439 rams), 8.7MN ± 3.1MN for the 2009 season (280 rams) and 8.2MN ± 3.4MN for the 2010 season (160 rams). Rams were conducted throughout the shipping season (July to October) at ship speeds from 4.1 to 15.6kt. The ramming activity, which occurred at latitudes from 68°N to 84°N, involved a wide range of ice thicknesses and strengths, which may partly explain why global impact forces did not decrease as the summer progressed. There was, however, a general trend of increasing global force with increasing ship speed.

The ram-related global forces for the six Regions were presented in terms of an encounter frequency. Only Region 2 (Peel Sound/Victoria Strait) and Region 6 (QEI/Banks Isl) provided enough data to comment on the global force associated with the ‘1 in 100 ram encounter frequency’: a 20MN global force could be expected for every 100 rams in Region 2 (during the second week of July) and a 15.7 to 18.9MN global force could be expected for every 100 rams in Region 6 (from late August to September). Global forces in the tail of the distribution ranged from 10 to 20MN, although a few of the rams produced forces well above the more “typical” rams, even though the ramming speed for the more significant collisions was on par with the less severe rams. This demonstrates that although most of the ice in the Arctic may be unremarkable, floes with appreciable thickness and/or strength can occur in any region, regardless of the time of year.

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List of Figures

Figure 1 Map showing the 16 Shipping Control Zones for the ASSPR ... 3

Figure 2 Six Regions where one or more ramming events occurred during the LSSL voyages .... 4

Figure 3 Data sources used to document LSSL voyages... 6

Figure 4 Schematic of MOTAN: sensor and software... 7

Figure 5 Location of MOTAN sensor with respect to VCG, LCG and centreline of LSSL ... 9

Figure 6 Rams with 11km diameter old ice floe in southern Beaufort Sea, 8 Aug 2009 ... 12

Figure 7 Representative weekly ice map of challenging ice encountered by the LSSL... 14

Figure 8 Images from the forward-looking camera on the LSSL... 16

Figure 9 Location of ramming events that occurred during past three LSSL voyages ... 17

Figure 10 Global impact forces on LSSL during 2008 season ... 19

Figure 11 Typical multi-year ice floe impacted during the Barrow Strait Ice Trials, Oct. 2008 21 Figure 12 Global impact forces on LSSL during 2009 season ... 23

Figure 13 Global force record for highest ramming speed noted during three Arctic voyages .. 25

Figure 14 Old ice floe that impeded the ship’s progress in the southern Beaufort Sea... 26

Figure 16 Ice features associated with some of the highest global forces in Region 6 ... 28

Figure 17 Global impact forces on LSSL during 2010 season ... 30

Figure 18 Ice floes associated with two rams in Region 5 during the first week of October... 31

Figure 19 Two ice features that required ramming about 200km offshore Banks Island ... 32

Figure 21 Three westbound transits through Region 2: ram-related global impact forces ... 35

Figure 22 Seasonal decrease in snow depth and ice thickness ... 36

Figure 23 Seasonal decrease in strength of sea ice... 36

Figure 24 Prototype map showing key areas where ridging most likely occurs ... 38

Figure 25 Three Arctic Voyages: ram-related global impact forces ... 40

Figure 26 Probability of exceedance plots for six Arctic Regions ... 42 Figure 27 Approaches used to calculate resultant forces... A-3 Figure 28 Trajectory of LSSL during 2008 season ... B-2 Figure 29 Dates on which LSSL brought 5 engines online during 2008 voyage ... B-3 Figure 30 Trajectory of LSSL during 2009 season ... C-2 Figure 31 Dates on which LSSL brought 5 engines online during 2009 voyage ... C-3 Figure 32 Trajectory of LSSL during 2010 season ... D-2

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List of Tables

Table 1 Particulars of CCGS Louis S. St-Laurent ... 8

Table 2 2008 Voyage: Number of Rams by Region and Time of Year ... 19

Table 3 2009 Voyage: Ramming Events by Region and Time of Year ... 23

Table 4 2010 Voyage: Ramming Events by Region and Time of Year ... 29

Table 5 Statistics of Ram-related Global Forces for Three Arctic Voyages ... 39 Table 6 Data Sources for 2008 Voyage ... B-2 Table 7 Data Sources for 2009 Voyage ... C-2 Table 8 Data Sources for 2010 Voyage ... D-2

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Monitoring Global Ice Impact Forces on the

CCGS

Louis S. St-Laurent: Interim Report

1.0 Introduction

The objective of this study is to obtain statistical information about the global forces on a vessel from impacts with sea ice and the ice conditions associated with those impact forces. This work has relevance to ships of all ice classes since the quantitative relation between ship impact forces and ice features (ice severity) will allow mariners to be better weigh the risks associated with navigating through ice regimes, or finding an alternate route. It will enable designers, engineers and mariners to characterize the ice conditions under which ships can operate safely, and those that are beyond the vessel’s capability (i.e. risk of damaging the ship).

Statistics have shown that 75% of the ship damage incidents in the Canadian Arctic result from ice conditions that had some concentration of multi-year ice (Kubat and Timco, 2003). A scoping study of 14 experienced Captains who operate vessels in the Arctic revealed the detection of multi-year ice as the most pressing area for future research, due to the high risk of damage that collisions with undetected multi-year ice pose for even ice-strengthened hulls (Timco et al., 2005). Consequently, this study focuses upon ‘challenging ice’ which is herein defined as ice conditions requiring the CCGS Louis S. St-Laurent, Canada’s foremost icebreaker, to back-and-ram to progress through the ice1. Typically, multi-year ice, second-year ice and ridged first-year ice present the most challenging conditions for the LSSL.

The work will also provide the metrics needed to quantify the how recent changes in Arctic ice conditions effect ship design requirements today, and in the near future. Of the more than 850 rams presented in this report, the events that occurred on 8 August 2009 best illustrate the importance of this work: the CCGS Louis S. St-Laurent spent more than two hours ramming a multi-year floe in the southern Beaufort Sea that was much stronger than expected – and which the ship could not avoid. The significance of this is that it shows how ice conditions in the Arctic are far from benign – and that even the most experienced mariners sometimes underestimate ice severity. Results from this project will better ensure that regulators, operators of ships, drill rigs, and offshore structures are prepared for the ice conditions they are likely to encounter in the Arctic.

An inertial measurement system called MOTAN is used to obtain statistical information about the global ice impact forces on the CCGS Louis S. St-Laurent (LSSL) during its annual voyages to the Arctic. Ice impact forces on the LSSL will be measured over a five-year period – the minimum length of time needed to obtain a statistically significant sample of ice loading events – in order to better quantify the effect of ice severity on ships. In this report, the interim results are presented for the three Arctic seasons for which data have been acquired and processed to date. The final results of this five-year project will be published in March 2014.

1

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The past three Arctic seasons of the LSSL are discussed in terms of the global impact forces from the hundreds of rams that occurred each season and their associated ice conditions. Various sources of data are used for the work, including Canadian Ice Charts, eye-witness accounts and images from a forward-looking camera.

2.0 Relevance to Shipping Regulations

Economic activity in the north is increasing, partly because ice conditions in summer are reported to be less severe. That places greater demands on Arctic shipping: there has been a 25% increase in the level of shipping activity in the North (B. LeBlanc, CCG personal

communication) and there is an increasing need to begin the shipping season earlier in the

summer, and extend it later in the fall. As Arctic regions become more accessible, mariners must have the knowledge and experience to navigate ice-covered waters with the utmost care and due diligence.

Transport Canada regulates navigation in Canada’s Arctic waters through the Arctic Shipping Pollution Prevention Regulations (ASPPR) which seeks to minimize the likelihood that a ship will enter and navigate in ice conditions beyond its safe operating limits. The Regulations provide two very different means of doing that: the Zone-Date System and the Ice Regime System. Each system is described below. Statistics on global ship impact forces and the associated ice conditions relate to both the Zone-Date System and the Ice Regime System by providing the kind of quantitative information needed to promote safe shipping and minimize the risk of pollution in ice-covered waters.

2.1 Zone-Date System

The Zone Date System, which came into effect in 1970, specifies the dates on which various ship types and classes can enter specific Shipping Control Zones. Since the Zone-Date System is based on the premise that nature consistently follows a regular pattern year after year, it is a rigid system that makes no allowance for the large inter-annual variations in ice conditions that naturally occur in the Arctic. Studies have shown that the Zone-Date System sometimes permits vessels to enter ice regimes that have a high potential of damaging the vessel and that, conversely, it often restricts vessels from entering regions where the ice conditions are favorable for a safe passage (Kubat et al. 2005, 2006, 2007).

Timco et al. (2009) show that existing boundaries of the 16 Zones in the Zone-Date System are quite representative of ice conditions in the Arctic, however the authors proposed changes to Zone 4 and consequently its two surrounding Zones (see Figure 1). The changes were suggested because the authors found that ice conditions in Zone 4 were quite severe in the years that the polar pack drifted south into the southern Beaufort Sea. The global impact forces measured during the 2009 voyage of the LSSL attest to that, as discussed later in this report.

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Figure 1 Map showing the 16 Shipping Control Zones for the ASSPR The red outline shows the revised zone boundaries for Zone 4, as discussed in the text

(after Timco et al., 2011)

2.2 Ice Regime System

The Ice Regime System was added to the ASPPR as a Regulatory Standard in 1996. It is meant to provide the flexibility needed to ameliorate two limitations inherent in the Zone-Date System: (1) allowing vessels to enter ice regimes that have a high potential of damaging the vessel and (2) restricting vessels from entering regions where the ice conditions are favorable for safe passage. The Ice Regime System does this by using an Ice Numeral (IN) to determine whether the ship should proceed through a Regime, or select an alternate route. The equation that is used to calculate the IN is given below.

.... ] [ ] [ + + = CaxIMa CbxIMb IN (1) where IN = Ice Numeral

Ca = concentration in tenths of ice type “a”

IMa = Ice Multiplier for ice type “a” and Ship Category (ASPPR 1989)

The term on the right hand side of the equation (a, b, c, etc.) is repeated for as many ice types as may be present in a Regime, including open water. The values of the Ice Multipliers reflect the capability of the vessel class to operate in different ice conditions without damage. If the

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calculated Ice Numeral is negative, the ship is not allowed to proceed into the ice regime. However, if the Ice Numeral is zero or positive, the ship is allowed to proceed with due care and diligence of the Mariner. Clearly, the IN is meant to take into account the amount of ice that is considered hazardous for the vessel (based upon the vessel’s ASPPR classification) and the vessel’s ability to navigate safely through that ice regime.

2.3 Six Regions used to Categorize LSSL Ramming Events

This report documents more than 850 rams from three voyages of the LSSL. Since most of the ramming events were concentrated in certain areas and absent from others, the data were categorized by the six Regions in Figure 2. The reader will note that these six Regions are different than the Shipping Safety Control Zones shown in Figure 1. The dotted lines in Figure 2 show the boundaries of the Shipping Control Safety Zones. For the purposes of this study, Regions 1, 4 and 6 are expanded versions of the Control Zones and Region 2 is a combination of Control Zones 4 and 6. It should also be noted that the Regions only include those areas where rams occurred; rams were not noted in areas outside the six Regions.

1 2 3 4 5 6 1 2 3 4 5 6

Baffin Bay/Lancaster Sound Peel Sound/Victoria Strait Coronation Gulf South Beaufort Sea Arctic Basin

Queen Elizabeth/Banks Isl.

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3.0 Sources of Data used for this Report

Various sources of data were used to document the Arctic voyages of the LSSL. First and foremost, the inertial measurement system called MOTAN was used to measure the ship motions from the time that the ship left port in mid-summer, until it returned to port in the fall. A variety of other data sources were equally important to this analysis because they provided a context for the MOTAN data. These sources include detailed GPS data (sampled at 1s), general GPS data (sampled hourly), the ship’s log books, ice charts, photographs and eye-witness accounts. As might be expected, compiling data from various sources often means that data are only available for certain periods of time or for some of the years. Figure 3 lists the duration of the

LSSL voyages each year, the data sources used to document the voyage and the periods for which

data were available. A detailed discussion of each of the data sources is presented in the following sections.

3.1 MOTAN

The National Research Council Canada’s Canadian Hydraulics Centre (NRC-CHC) developed an inertial measurement system called MOTAN as an alternate approach to measuring global impact forces on ships, compared to the more traditional approach of installing strain gauges throughout the ship’s framework. MOTAN, which stands for MOTion ANalysis, was initially developed to measure the motions of ships and floating structures in a wave basin or towing tank (Miles, 1986) but has since undergone extensive modifications to permit its use for estimating the global force of ship-ice interactions at full-scale. Results from the first full-scale deployment on the USCGC Healy showed that MOTAN could be used to reliably to calculate ice-induced global impact forces from full-scale ship motions (Johnston et al., 2001). Since that time, MOTAN has been used on a number of ice-strengthened ships to refine and improve the system (Johnston, 2006). The full-scale program on the CCGS Terry Fox has been the most comprehensive validation study of MOTAN to date, whereby impact forces from MOTAN were compared to force measurements from two other, independently operated systems (Johnston et al., 2008-a, 2008-b).

Figure 4 shows that the MOTAN system consists of two parts (1) a physical sensor to measure ship motions in six degrees of freedom and (2) specially developed software to calculate first, the whole-ship motions and second, the global exciting forces and moments induced by ship-ice interactions. The physical MOTAN sensor has three accelerometers and three rotational rate sensors to measure respectively the ship’s total acceleration, including earth’s gravity component, and its three-dimensional angular rotational rates, each of which is resolved along the instantaneous positions of the X, Y and Z body-axes of the ship. The six analog voltage signals from MOTAN are recorded by a standard data acquisition system. MOTAN is equipped with a low-pass hardware filter to remove vibrations higher than 5Hz, since those frequencies are not characteristic of the ship’s global response to impacts.

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2008 voyage MOTAN data GPS detailed GPS general, SailWx Weekly ice maps "Time on Task" Ram-related photos, mast camera 2009 Arctic voyage MOTAN data GPS detailed GPS general, SailWx Weekly ice maps "Time on Task" Ram-related photos, mast camera 2010 Arctic voyage MOTAN data GPS detailed GPS general, SailWx Weekly ice maps "Time on Task" Ram-related photos, mast camera

Wk-2 Wk-3

July August September October November

Wk-2 Wk-3 Wk-4 Wk-1 Wk-2 Wk-3 Wk-4 Wk-1

Wk-1 Wk-2 Wk-3 Wk-4 Wk-1 Wk-2 Wk-3 Wk-4 Wk-1

Figure 3 Data sources used to docum

ent

LSSL

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MOTAN

Rate Acceleration

Physical Sensor:

3 accelerometers & 3 angular rate sensors dimensions: 260 mm x 160 mm x 100 mm weight: 1.88 kg Computer Software Displacement Surge x x x Sway y y y Heave z z z Pitch θ θ θ Roll φ φ φ Yaw ψ ψ ψ x ’ y’ z’ Heave Pitch Roll Yaw Sway Surge

arrows used to show coordinate system and (positive) sign convention

MOTAN10

Whole-ship Motions (displacements,rates and accelerations)

EFM

Global Impact Forces (determined using output

from MOTAN10)

a b

Figure 4 Schematic of MOTAN: sensor and software

3.1.1 MOTAN10: Software for Calculating Whole-ship Motions

Specially developed software2 called MOTAN10 is used to solve the nonlinear equations of motion to relate the 18 motion components (see Figure 4) to the body-axes accelerations and rotational rates measured by the six MOTAN inertial motion sensors. Appropriate calibration coefficients are needed to convert the raw data from the three accelerometers from volts to m/s² and raw data from the three rotational rate sensors from volts to deg/s. Once converted, the raw data signals were input into the MOTAN10 software, where bounds were placed on the upper and lower frequency content of the signal for computing the 18 components of whole-ship motions noted in Figure 4. Previous installations of MOTAN have shown that a lower bound of 0.05Hz and an upper bound of 2.0Hz capture the full content of the whole-ship motions. It is well known that frequencies above 2.0Hz are caused by secondary ship vibrations (Chen et al., 1990), which makes them irrelevant to global ship accelerations. Setting a lower frequency limit is more challenging however, since the lower frequency cut-off does affect the magnitude of global impact force.

In order to calculate the global impact force for a rigid body, the whole-ship motions must be calculated at the ship’s centre of gravity. That requires translating the accelerations and rotational rates measured by the MOTAN physical sensor from the place where the sensor was installed (close to the centre of gravity) to the vertical centre of gravity (VCG), longitudinal centre of gravity (LCG) and the ship’s centreline. When MOTAN was installed on the LSSL in July 2008, the distance of MOTAN to known reference points along the X, Y and Z axes of the ship were measured so that the data from sensor could be later translated to the ship’s centre of

2

MOTAN10 was developed in 2008 in preparation for this research project. MOTAN10 is an improved version of software for calculating the whole-ship motions on full-scale ships. Comparison of results from MOTAN10 and MOTAN7A (the previous version) for select cases from the CCGS Amundsen data showed improved results in some respects, but the software still appears to have some limitations, as discussed in Johnston (2012).

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gravity. Figure 5 shows the distance of MOTAN from the ship’s centreline, as well its distance from the VCG and LCG corresponding to ‘Condition 2: Loaded Departure’ which was considered to be the ship’s most representative condition throughout most of the voyage (see Table 1). The particulars of Condition 2 for the LSSL had been provided to the author by the Chief Engineer of the LSSL when MOTAN was installed to supplement measurements from the propeller deflection trials in October 2001 (Johnston et al., 2001).

3.1.2 EFM: MOTAN Software for Calculating Global Impact Forces

The MOTAN software EFM, for Exciting Forces and Moments (Figure 4) is key to using an inertial measurement system to calculate global forces on ships from impacts with ice. In effect, the EFM software uses the entire suite of whole-ship motions and information about the ship’s particulars, to back-calculate the force that would have been required to produce the measured ship’s response. EFM uses the six linear coupled differential equations included in Salvesen et al. (1970) and McTaggert (1997) to calculate three global exciting forces and three global exciting moments at the ship’s origin. Calculating the exciting forces and moments with EFM requires information about the ship’s characteristics, as well as its hydrodynamic coefficients and hydrostatic coefficients, as described in McTaggert (1997). These coefficients were developed for the LSSL for a wide range of frequencies at operational ship speeds from 1 to 12kt (0.5 to 6.2m/s) for Condition 2 “Loaded Departure”. Appendix A includes a more detailed discussion of the two approaches that EFM uses to calculate global impact forces.

Table 1 Particulars of CCGS Louis S. St-Laurent Design Particularsa

Length overall 119.6 m

Beam 24.4 m

Total Power _{36.2 MW}b

Particulars for Condition 2c:

Displacement 12874 t

Draft at amidships 8.80 m LCG, longitudinal centre of gravity, fwd of AP 49.24 m VCG, vertical center of gravity, above keel 8.56 m

a _{design particulars obtained from Canadian Coast Guard website}

b

personal communication Captain S. Julien;

rated power 29.4MW, personal communication Captain T. Potts

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8.8 m, draft at midship centreline + centre of gravity 110 m 4.8 m 8.6 m 1.7 m aft perpendicular (AP) forward perpendicular (FP) AP FP 4.8 m fwd of LCG 2.2 m above VCG 1.7 m port of centreline 4.8 m + 2.2 m

Figure 5 Location of MOTAN sensor with respect to VCG, LCG and centreline of LSSL

3.1.3 Autonomous MOTAN Operation for LSSL

Many installations of MOTAN, including recent measurements on the CCGS Amundsen, benefited from having NRC-CHC personnel on the bridge to ‘mark’ when impacts occurred, as described in Johnston (2012). Typically, this was done by using a small, hand-held device to send a signal from the bridge to the data acquisition system each time an event of interest occurred. Photographs of the event-related ice feature were taken and notes were made about the ship’s response and the general area of the ship’s hull that had been impacted, when possible. That full compliment of information was used to examine a relatively small number of ship-ice impacts on a case-by-case basis. At the outset of this project, it was realized that examining events on a case-by-case basis for the LSSL would not be feasible for processing MOTAN data for the entire Arctic voyage – nor would it be possible for NRC personnel to be onboard to conduct detailed observations of the hundreds, or thousands, of ice impacts that occurred each year. The statistical nature of this LSSL project required developing a MOTAN system that could operate autonomously.

The so-called ‘autonomous MOTAN’ system was designed to log data continuously throughout the ship’s entire voyage. This required upgrading the data acquisition system to permit the storage of large volumes of data from MOTAN’s six inertial sensors (sampled at 20Hz), as well as a continuous record from the global positioning system (GPS data, sampled at 1Hz) for the duration of the voyage. The autonomous MOTAN system would also need to restart automatically if power to the unit failed at any time, since personnel would not be available to check on the system. Considerable effort was also devoted to developing computer subroutines

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to automatically identify ice-related impacts from the wealth of open water data that were not of interest3. To assist with the data analysis, a ‘peak detection routine’ was developed to identify impact events and a ‘ramming routine’ was developed to identify ice-related ramming events. Unfortunately, the peak detection routine could not differentiate ice-impact events from rough open water events and the ‘ramming routine’ identified less than 50% of the ship rams that actually occurred during the ship’s voyage. Since neither automated technique was satisfactory, the results in this report were obtained by manually identifying ramming events from MOTAN data, which were subsequently cross-checked with various sources of data to confirm that the ice-related ram had indeed occurred.

To date, this work has focused upon ship encounters with challenging ice that required one or more rams to progress through the ice. This report does not consider global forces from ‘transient’ impacts, which are defined here as very short duration impacts that do not require one or more rams. That said, it should be noted that transient impacts can produce substantial global forces on the ship, as illustrated by many of the time-series traces in the Appendices. It is also noteworthy that rams are taken on the ship’s bow, but transient impacts can involve areas of the hull that are more vulnerable to damage than the ship’s bow. Identifying transient impacts from the continuously acquired MOTAN data will require developing improved subroutines to automate the process because there will be thousands of transient impacts during each voyage, rather than the hundreds of rams discussed in this report.

3.1.4 Time-series Records of Global Impact Forces

In this report, single rams are identified as instances where the ship increased speed from a near stopped position until it attained a speed of up to 15kt to impact an ice feature. Repeated rams are defined as those instances where the ship backed away from the floe and then proceeded to impact the floe more than once. Single rams and repeated rams are clearly identifiable in the global impact force records from MOTAN when the ship speed is superimposed, as shown in Figure 6-a. The figure shows a portion of the time series trace from repeated rams with an 11km diameter aggregate floe of second-year and multi-year ice. The LSSL rammed this floe for just over two hours. A total of 26 rams were required before reaching an area where the ship could turn out of the floe and go around it. The aerial photograph in Figure 6-b shows the area of ice where the LSSL extricated itself from the floe. Two of the highest forces of the 2009 season occurred during rams with this floe and ram #12 in Figure 6-a produced the highest global impact force for Region 2 (25.4 MN) of the three LSSL voyages.

Repeated ramming produces a characteristic pattern in the MOTAN data and ship speed. Rams with strong ice, which do not allow the ship to penetrate very far into the floe, usually produce the highest impact force shortly after the ship contacts the ice. Conversely, when the ship encounters weaker ice at the floe’s edge, it penetrates well into the floe and, often, the highest impact forces occur well after the initial ship-ice contact. Surprisingly high impact forces can occur as the ship penetrates further into the floe, as many of the MOTAN records in the Appendices illustrate.

3

MOTAN is not appropriate for calculating wave-induced global forces, so the ship’s open water response is not of interest in this regard.

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The three rams depicted in Figure 6-a each were conducted at a maximum speed of 10kt and lasted about one minute. The ship increased speed until contacting the ice, then slowed until coming to a halt. As the ship came into contact with the floe, its speed could decrease very abruptly (seconds) if the ice was solid and permitted minimal penetration, or over a period of minutes if the ice was soft and allowed greater penetration. Having completed one ram, the ship backed off the floe (if ride-up was significant) and reversed to a distance of one or more ship lengths in preparation for a second ram. Generally, forces measured during the backing portion of the ramming cycle were minimal (less than 1MN), that is unless the ship backed into a solid piece of ice – which is strictly avoided because it risks damaging the propellers.

The floe that the LSSL encountered on 8 August 2009 provides an excellent example of a multi-year floe that did not appear formidable upon first inspection, but proved to be once the ship ventured into the ice. Initially, this multi-year floe was believed not to have posed a serious impediment to the ship’s progress, however that proved not to be the case after two hours of ramming resulted in the ship’s penetrating the floe by only a few ship lengths. Since it may not always be possible to back out of the floe, the Commanding Officer is committed to proceeding through the floe until finding a route out of the ice. Very likely, this is an experience that all Commanding Officers of icebreaking ships will encounter at least once in their career (Captain J. Broderick, personal communication).

3.2 Global Positioning System (GPS)

Detailed records from the global positioning satellite (GPS) proved essential for determining when and where rams occurred. The ship’s position was logged at a sampling interval of 1s, from which the speed of the ship (over ground) was calculated. A five second running average was used to smooth the calculated ship speed, and then the speed record was superimposed on the 4-hour long MOTAN force records. The ship speed that was derived from the GPS is meant to relate to the MOTAN impact forces in a general way, since the GPS data are sampled at 1Hz. As a result, in the subsequent discussions, the maximum speed attained during the ram is reported, rather than the ship’s speed at the instant that the peak force occurred. This is partly done to minimize the problems associated with synchronizing timestamps to a fraction of one second. Processed accelerations from MOTAN (which are sampled at 20Hz) are far superior to the GPS data (sampled at 1Hz) for describing the effect of an impact on the ship.

The detailed ship trajectory was mapped with geographic information software (GIS) to determine where repeated rams occurred and, in some cases, to quantify the penetration distance attained during each ram. Figure 6-c shows the zigzag pattern that characterizes repeated rams, as the ship impacts the floe, then retreats for another ram. The zigzag pattern can either indicate that the floe is drifting and that the ship moves also as it continues impacting the same general area of ice, or that the Commanding Officer has decided to impact the floe in a different location for each ram. The number of rams per kilometer directly relates to the time needed to progress through the ice – which could also be interpreted as “ice severity”. In some cases, a single ram was needed for the ship to progress through a continuous ice sheet or to break an isolated floe in open water, however aggregate floes like the one in Figure 6-c required repeated ramming to advance through the ice.

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Figure 6 Rams with 11km diameter old ice floe in southern Beaufort Sea, 8 Aug 2009 (a) ship speed & MOTAN impact forces, (b) portion of the multi-year floe that was transited prior to

turning out of the floe and (c) ship ramming track (photo courtesy of B. Molyneaux, Canadian Ice Service)

2800 2900 3000 3100 3200 3300 0 5 10 15 20 25 30 Gl ob a l i m p a c t fo rc e ( M N) & s h ip sp ee d (k t) Time (seconds) impact force ship speed (ram #9) ship speed (ram #10) ship speed (ram #11) ship speed (reverse) (a) (b) (c) 0 200 m Ram #1 Ram #2 Ram #26

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3.2.1 Sources of GPS Data for Ship Speed and Ramming Track

Various sources of GPS data have been employed during the past three years, ranging from a stand-alone GPS that was logged independently of the MOTAN data acquisition system to one that directly fed into the MOTAN system. A stand alone GPS was used during the 2008 season. Since data from MOTAN and the GPS were logged by separate computers, it was extremely difficult to synchronize their timestamps to the fractions of second that were needed to relate the ship speed to MOTAN data, photographic images, etc. The problem of synchronizing the timestamps of separate data systems has plagued many research projects. It is absolutely essential that a common time base be used when comparing data from various sources.

The problem of not having a common time base was remedied during the 2009 and 2010 voyages because GPS data were obtained directly from the ship’s network. The satellite-based timestamp was written directly to the MOTAN data acquisition, which was very beneficial, but it introduced a different problem: during the first year, writing the GPS string of data directly to the MOTAN system caused the data acquisition system to reach maximum capacity on 30 September, about two months before the LSSL returned to port. As a result, neither MOTAN data nor detailed GPS data are available for the eastbound transit of the NWP (October, see Figure 3).

That problem was remedied before the next season, but then a different, equally frustrating problem arose for the 2010 season. During the 2009 season, the ship’s GPS was believed to have been the data source, however that proved not to be the case when large gaps appeared in the GPS data downloaded at the conclusion of the 2010 season. Only then, was it realized that data were being acquired from the science GPS that had been installed by the Canadian Hydrographic Service (CHS) for the UNCLOS mission, which was not put in place that year until 25 August. Therefore, detailed GPS data are not available for the westbound transit of the NWP (see Figure 3). Since MOTAN data alone were used to identify ramming events (without ship speed and ship track information), the confidence associated with the 16 rams for the 2010 westbound transit of the NWP is quite low. There is no corresponding information about the speed at which those rams occurred, which is why the ship’s surge acceleration was substituted for the ship speed in some of the time-series traces for the 2010 season (Appendix D).

3.2.2 SailWx: GPS Data for General Ship Track

During the portions of 2009 and 2010 voyages for which detailed GPS data are unavailable, the general location of the ship was obtained from the SailWx website (http://www.sailwx.info/shiptrack). Since the information on the SailWx website is posted only once per hour, the data are not suitable for determining ship speed nor are they detailed enough to use the ship’s track to determine where ramming occurred. The absence of this information makes identifying instances of ramming events from the MOTAN data alone extremely challenging. So, although the independently operated GPS may have been difficult to synchronize with the MOTAN data during the 2008 season, it provided the most complete detailed GPS record of the three seasons (Figure 3).

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3.3 Weekly Maps of Challenging Ice

For this study, weekly ice maps, in combination with MOTAN data, were used to define where the LSSL encountered challenging ice. Figure 7 illustrates the type of ice map that was used to represent, in a general way, the concentration of old ice (second-year and multi-year ice) encountered by the LSSL during each week of its voyage. The ice maps were derived from the weekly Regional Ice Charts issued by the Canadian Ice Service. This kind of ice map has limitations because (1) it uses the ice conditions on one particular day to represent the conditions for the entire week and (2) it depicts only the concentration of old ice rather than the total ice concentration (which includes first-year, second-year and multi-year ice). At the outset of this study, old ice was believed to represent the greatest obstacle to the LSSL during its summer voyage (July to October). Note that the blue color in the maps does not mean open water – it indicates less than 1/10th concentration of old ice. The old ice concentration in the weekly ice maps was classified according to the same categories used by the Canadian Ice Service in their Regional Ice Charts for the Eastern and Western Arctic:

(1) less than 1/10th concentration of old ice – blue color (2) 1 to 3/10ths concentration of old ice – green color (3) 4 to 6/10ths concentration of old ice – yellow color (4) 7 to 8/10ths concentration of old ice – amber color (5) 9 to 9+/10ths concentration of old ice – red color (6) 10/10ths concentration of old ice – dark red color

1 2 3 4 5 6 10/10ths Old ice 9 to 9/10ths Old ice 7 to 8/10ths Old ice 4 to 6/10ths Old ice 1 to 3/10ths Old ice <1/10th Old ice

dotted line shows extent of coverage in CIS Regional Ice Charts

Figure 7 Representative weekly ice map of challenging ice encountered by the LSSL (only old ice concentrations are depicted in this map; CIS Regional Ice Charts for Eastern Arctic and

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The various categories range from the near absence of old ice (“less than 1/10th”) to the complete coverage of old ice (“9 to 9+/10ths” and “10/10ths”). The concentration of first-year ice is not accounted for in Figure 7, except to say that first-year ice and/or open water comprise the remainder of the ice when old ice concentrations are equal to “7 to 8/10ths”, or less. The weekly old ice maps for each week of the 2008, 2009 and 2010 voyages are included in the Appendices.

3.4 ‘Time on Task’ Documentation

The Canadian Coast Guard (CCG) had compiled material from the LSSL’s logbook to relate fuel consumption to the ice conditions encountered. Their interest in performing this investigation was to determine machinery and equipment configurations and realistic design requirements for the new Polar Icebreaker (Captain S. Julien, personal communication). The so-called ‘Time on Task’ documentation is also relevant to this study because it details the number of hours that various configurations of the LSSL’s five engines were brought online to complete various operational tasks. Since the number of engines brought online was directly related to the presence of ‘challenging ice’, the information can be used verify on which days the ice maps and MOTAN data indicate that the LSSL encountered difficult ice conditions. The ‘Time on Task’ documentation is available for the 2008 and 2009 seasons only (see Figure 3) and is included in Appendices B and C respectively.

3.5 Forward-Looking Camera

Images from the forward-looking camera that the University of Alaska installs on the LSSL each year were provided for the purposes of this study (J. Hutchings, personal communication). The forward-looking camera is installed high on the ship’s mast, where it collects time-lapse photos of the ice conditions throughout the ship’s voyage. These images are usually only available for the Beaufort Sea, since that is the focus of Dr. Hutchings research project. During the 2008 and 2009 seasons, the images were taken at 10 minute intervals; during the 2010 season the images were acquired at intervals from 10 seconds to 30 minutes.

The timestamp that was printed on each image was cross referenced to the MOTAN ramming events so that the images could be used to document the ice features associated with the highest global impact forces logged during the season. Unfortunately, fog and sometimes darkness obstructed the image clarity during the rams. That was especially true for the high Arctic, as shown in Figure 8-a, which is unfortunate because some of the highest impact forces were measured in this region. Although the ram-related images usually did not coincide with the exact time of the ram event, they often contained evidence of the LSSL’s bow print (see Figure 8-b), particularly when repeated ramming was needed to progress through the ice.

Due to a problem with synchronizing the time base of MOTAN data acquisition system to the independent GPS, it is difficult to accurately cross reference the forward-looking images for the 2008 season. The 79 images from the forward-looking camera that were clear enough to link the ice features with results from MOTAN revealed little correlation: where global impact forces from MOTAN and the detailed GPS records indicated that the ship was transiting ice, sequential

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images revealed that the LSSL was not moving. Results for the 2009 and 2010 seasons were better. A total of 94 ram-related images and 11 ram-related images were clear enough to be linked to MOTAN data for the 2009 and 2010 seasons, respectively. It is reasonable to expect that the ice features in the images would have caused the ship response measured by MOTAN. Here it should be mentioned that for large portions of the LSSL voyage in the Beaufort Sea, the crushed debris in front of the ship was created by the USCGS Healy – in fact many of the forward-looking images show the USCGC Healy leading the LSSL. The two ships operated in tandem throughout extensive areas of the Beaufort Sea (Region 4), Arctic Basin (Region 5) and NW Islands (Region 6, see Figure 2). The USCGC Healy was often in the lead because it provided a broken channel for the LSSL to tow its seismic array. However, the LSSL would take the lead during the most challenging ice conditions. Since this report focuses on challenging ice – specifically where ramming was required to progress through the ice – the statistics for these three regions may not have been substantially altered by the LSSL following the USCGC Healy.

Figure 8 Images from the forward-looking camera on the LSSL

(a) image from high Arctic that was obstructed by fog and (b) image from lower Arctic showing bow print left by ramming the multi-year floe

(images courtesy of J. Hutchings, University of Alaska)

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4.0 Voyages of CCGS Louis S. St-Laurent

The following sections document the three Arctic voyages of the LSSL in terms of the number of ramming events that took place, where they occurred, their associated ice conditions and the magnitude of the global impact forces. The map in Figure 9 is a compilation of the three years of data, categorized by the six Regions in which the ramming events took place. The detailed discussion in the sections below provide the context needed to better understand the ramming activity in each Region, and the global forces caused by those impacts.

The reader is referred to the Appendices for the full compliment of data compiled for each of the three voyages. There, the ship track is provided for the entire voyage, along with tables of the periods for which data from various sources were available, weekly ice maps, ‘Time on Task’ documentation and the time-series records of ship speed and global impact forces for the individual rams. It should be noted that many of the rams in Regions 5 and 6 were outside the areas covered by the CIS Regional Ice Charts (see Figure 7). The MOTAN time-series traces of global force in Appendices B, C and D include thousands of impacts that did not result from single or repeated rams, therefore are not discussed here.

1

2

3

4

5

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1 2 3 4 5 6

Baffin Bay/Lancaster Sound

Peel Sound/Victoria Strait Coronation Gulf South Beaufort Sea Arctic Basin

Queen Elizabeth/Banks Isl. 2008 LSSL Voyage (439 rams) 2009 LSSL Voyage (276 rams) 2010 LSSL Voyage (160 rams)

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4.1 2008 Voyage

The LSSL departed from the port of Halifax en route to the high Arctic on 4 July 2008 and returned to the port of Halifax on 19 November (see Appendix B). MOTAN data are available for the entire duration of the voyage, as are detailed GPS data, apart from a few days in October and the last two weeks of November. Judging from the MOTAN data and weekly ice maps, ramming activity was not expected to have occurred during the periods for which detailed GPS data were not available.

The ‘Time on Task’ for the 2008 voyage indicated that the ship was steaming for 80.2% of the 3305 hours (139 days) spent at sea. The percentage of time spent in the various engine configurations was 10% for one engine, 55.2% for two engines, 23.6% for three engines, 2.7% for four engines and 7.5% for five engines (Captain S. Julien, personal communication). Appendix B shows the dates on which five engines were used during the 2008 voyage.

A total of 439 rams were conducted during the 2008 voyage. The number of ramming events that took place while the ship operated in the various regions is listed in Table 2, as are the instances where ramming was not needed. A significant amount of activity took place during the ship’s westbound transit of Region 2 (Figure 9) and during the three weeks that the ship operated in Region 6 (Figure 9). Apart from those two regions, ramming was not required for most of the transit. That said, the time series records of global impact force in Appendix B clearly show that thousands of transient impacts occurred as the ship transited ice-covered waters – and that the global forces from the transient impacts sometimes rivaled the ram-related impact forces.

Figure 10 plots the ram-related global forces according to the Region in which they occurred and the time of year. Two of the three highest ram-related global forces of the 2008 voyage occurred in September in Region 6 (26.9MN, 23.1MN) and the third occurred in mid-July in Region 2 (25.4MN). The considerable amount of scatter in the data is to be expected, since the rams took place at a range of speeds, were characterized by various ship-ice contact areas and involved ice of different thickness and strength. It is also important to note, however, that global impact forces were appreciable for impacts that occurred throughout the voyage, regardless of whether it was mid-summer or late fall. The average global force of the 439 rams was 10.5MN ± 3.4MN.

4.1.1 Region 1: Baffin Bay and Lancaster Sound

The LSSL operated in Region 1 only during the second week of July, as it transited north. Eight rams were conducted in Region 1 from 10 to 11 July. Global impact forces for the 8 rams ranged from 7.5 to 17.2MN for impact speeds of 8.6 to 13.4kt. The weekly ice maps indicate that one ram was needed while transiting Baffin Bay (1 to 3/10ths concentration of old ice) and seven rams were needed in Lancaster Sound (less than 1/10th old ice).

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Table 2 2008 Voyage: Number of Rams by Region and Time of Year

2008 Voyage (439 rams) Region 1 Region 2 Region 3 Region 4 Region 5 Region 6

Jul - Wk1 Jul - Wk2 8 166 Jul - Wk3 0 0 Jul - Wk4 0 Aug - Wk1 2 Aug - Wk2 0 Aug - Wk3 0 Aug - Wk4 0 0 Sep - Wk1 0 Sep - Wk2 126 Sep - Wk3 104 Sep - Wk4 13 Oct - Wk1 0 0 Oct - Wk2 20 Oct - Wk3 0 0 5 10 15 20 25 30

05 Jul 15 Jul 25 Jul 04 Aug 14 Aug 24 Aug 03 Sep 13 Sep 23 Sep 03 Oct 13 Oct

Day/Month on which ship ram occurred

G loba l i m pa c t f or c e ( M N ) 2008 (n = 439) Region 2 Region 5 Region 6 Region 2

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4.1.2 Region 2: Westbound Transit through Peel Sound and Victoria Strait (July)

In 2008, the LSSL made its westbound transit through Region 2 during the second week of July, which is one to two weeks earlier than most years. A total of 166 rams were conducted from 12 to 17 July (Wk-2) as the ship transited less than 1/10th old ice concentration. The Ice Service Specialist (ISS) aboard the LSSL characterized the ice conditions during the transit as follows: “thick first-year ice was predominant from Lancaster Sound to Cambridge Bay. There was some multi-year ice Barrow Strait and Larsen Sound. Much of this ice is undergoing melt in various stages from a few puddles to rotten. Some remnants of snow cover were observed.” Unfortunately, images from the forward-looking camera were not available for this period. Correspondence from the Canadian Coast Guard indicated that the period from 13 to 16 July provided a good 4-day average of fuel consumption in ridged and level first-year ice in a full power configuration (Captain T. Potts, personal communication). The ‘Time on Task’ documentation in confirms that five engines were used for much of the transit through Region 2. The northern entrance to Peel Sound was especially challenging in mid-July since nearly 100 rams were required in that area, as was the entrance to M’Clintock Channel, where 130 rams were conducted. Global impact forces for Region 2 ranged from 4.9 to 25.4MN in mid-July, for impact speeds from 9.2 to 14.3kt.

4.1.3 Region 2: Eastbound Transit through Peel Sound and Victoria Strait (October)

No rams were needed during the eastbound transit through Victoria Strait and Peel Sound in mid-October. The 20 rams that are noted in Table 2 for the westbound transit of Region 2 were actually conducted in Barrow Strait on 14 and 15 October 2008 as part of the “LSSL Hull Girder Strength Evaluation Trials”. The objective of the trials was to compare baseline values of the strains induced by typical Arctic icebreaking conditions to the strains from rough open water, in order determine the most likely cause of structural damage observed in the hull (Steele, 2009). A total of 10 head-on symmetrical rams were conducted at speeds from 5 to 10kt during the trials, as well as 13 port side impacts conducted at speeds from 3.6 to 11kt. These impacts focused upon two immense, old ice floes, one of which is pictured in Figure 11. A second-year ice floe (2.5 miles across) with embedded multi-year ice floes (500 to 1000 m across) was the object of attention on the first day. The second day of tests involved an even larger second-year floe (6.3 miles across) with embedded multi-year ice floes. The average thickness of the second-year ice was estimated to be about 3 m and the multi-second-year ice was estimated to be about 4 m thick (Steele, 2009). Ridges more than 6 m thick were rammed and dismantled on 14 October. The ice conditions encountered during the Trials were far from limiting for the LSSL since the old ice was relatively thin and its strength was expected to be well below the peak mid-winter value, as noted by Steele (2009).

The MOTAN–derived global impact forces for the 20 rams cited in this report ranged from 4.1 to 19.8MN for ship impact speeds from 5.1 to 11.5kt. To date, global impact forces from the strain gauge measurements have not been made available, since that was not the focus of the study (C. Oldfield, personal communication). Data from the ‘Time on Task’ indicate that five engines were used for portions of the Hull Girder Strength Evaluation Trials on 14/15 October (see Appendix B).

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Figure 11 Typical multi-year ice floe impacted during the Barrow Strait Ice Trials, Oct. 2008 (after Steele, 2009)

4.1.4 Region 3: Coronation Gulf

At no time during the three different occasions that the LSSL transited Region 3 was ramming required to progress through the ice. The transits were made during the third week of July en route to the Beaufort Sea, during the fourth week of August likely to conduct a crew change from Kugluktuk and during the first week of October for an eastbound voyage through the NWP. The concentration of old ice was less than 1/10th each time the LSSL operated in this region.

4.1.5 Region 4: Southern Beaufort Sea

The LSSL operated in the Southern Beaufort Sea during the third week of July, the third week of August and the first week of October. Old ice concentrations in this area ranged from less than 1/10th to 4 to 6/10ths at most, when the LSSL transited the Region. No rams were needed to transit the ice in this region at any time during the 2008 voyage.

4.1.6 Region 5: Arctic Basin

The LSSL operated in the Arctic Basin from late July to early August, and from late August to early September. Only two rams occurred in this Region, both of which took place on 4 August in the high Arctic (Figure 9). The rams produced global impact forces of 11.1MN (6.0kt impact speed) and 14.8MN (4.7kt impact speed). The weekly ice maps provide no information about the ice conditions in this area of Region 5 because it was beyond Canadian Ice Service’s coverage. It should be noted that the absence of ramming activity in this Region may have been due to the fact that the LSSL followed the USCGC Healy much of the time while in Region 5.

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4.1.7 Region 6: Queen Elizabeth and Banks Islands

The LSSL operated in Region 6 during the second week of August and for three weeks in September. No rams occurred during the second week of August, but a total of 126 rams were conducted during the second week of September, 104 rams during the third week of September and 13 rams during the fourth week of September. The rams in this Region produced two of the highest global impact forces during the 2008 voyage (26.9MN, 23.1MN, see Figure 10). Global impact forces for this Region ranged from 4.3 to 26.9MN for impact speeds from 7.2 to 12.7kt. The average global impact force for the three weeks of ramming was 9.8MN (Wk-2), 9.5MN (Wk-3) and 8.5MN (Wk-4). Data from the ‘Time on Task’ indicate that five engines were required during periods of 11 to 13 September and from 18 to 19 September.

4.2 2009 Voyage

The map of the entire 2009 voyage of the LSSL shows that the ship departed for the Arctic on 13 July 2009 and returned on 17 November (see Appendix C). MOTAN and detailed GPS data cover the period from 13 July to 30 September but are not available for late season operations in the Beaufort Sea nor the return transit through the NWP because the capacity of the data acquisition system filled on 30 September, as discussed previously.

The ‘Time on Task’ for the 2009 voyage notes that 78.8% of the 2904 hours (122 days) at sea was spent steaming. The percentage of time spent in the various engine configurations was 5.9% for one engine, 70.2% for two engines, 17.6% for three engines, 4.7% for four engines and 1.7% for five engines (Captain S. Julien, personal communication). Appendix C shows the dates on which five engines were used during the 2009 voyage.

A total of 280 rams were conducted during the portion of the voyage for which data are available. Most of those rams took place in Region 6 (Figure 9) resulting in an average peak global force of 8.7MN ± 3.1MN. Table 3 gives a breakdown of the number of rams that occurred in each Region; Figure 12 shows the peak global forces that were measured at different times of year in each Region. The two highest ram-related global forces of the season occurred in the southern Beaufort Sea (Region 6) on 8 August. The following discussion presents the pertinent details of the ramming activity for the 2009 voyage.

4.2.1 Region 1: Baffin Bay and Lancaster Sound

Ramming was not needed to progress through the less than 1/10th concentration of old ice as the

LSSL transited Region 1 during the fourth week of July. The ship made the return trip through

Region 1 during the third and fourth weeks of October, when it sometimes passed through old ice concentrations up to 4 to 6/10ths but ramming was not required.

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Table 3 2009 Voyage: Ramming Events by Region and Time of Year

2009 Voyage (280 rams)* Region 1 Region 2 Region 3 Region 4 Region 5 Region 6

Jul - Wk1 Jul - Wk2 Jul - Wk3 Jul - Wk4 0 Aug - Wk1 14 4 Aug - Wk2 26 0 Aug - Wk3 1 6 Aug - Wk4 227 Sep - Wk1 0 Sep - Wk2 0 Sep - Wk3 0 0 0 Sep - Wk4 0 2

Oct - Wk1 n/a n/a

Oct - Wk2 n/a n/a n/a

Oct - Wk3 n/a n/a

Oct - Wk4 n/a

*MOTAN data and detailed GPS data were not available after 30 September, as indicated by “n/a”

0 5 10 15 20 25 30

27 Jul 06 Aug 16 Aug 26 Aug 05 Sep 15 Sep 25 Sep 05 Oct

Day/Month on which ship ram occurred

G lo b al i m p a ct f o rce ( M N ) 2009 (n = 280) Region 2 Region 6 Region 4 Region 2

Figure 12 Global impact forces on LSSL during 2009 season (MOTAN and detailed GPS data are not available after 30 September)

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4.2.2 Region 2: Peel Sound and Victoria Strait

The LSSL made its westbound transit through Region 2 during the first week of August, about one week later than normal. A total of 14 rams were needed to transit areas of old ice concentrations up to 4 to 6/10ths. Nearly all of the ramming activity in Region 2 occurred where M’Clintock Channel entered into Victoria Strait. The ‘Time on Task’ compilation indicated that five engines were required on 1 August, which corresponds to the date on which nine of the rams were conducted in Region 2. The Ice Service Specialist (ISS) onboard the ship during the transit recalled several “moderate hits” during the transit through Peel Sound (A. Pelland, personal communication). Images from the forward-looking camera were not available for this period. Peak global forces for the 14 rams in Region 2 ranged from 2.9 to 11.3MN for speeds from 6.9 to 9.5kt.

The ship’s eastbound passage through Region 2 was made during the third week of October. The ice maps show old ice concentrations up to 7 to 8/10ths at the northern entrance to Peel Sound (Appendix C) but since MOTAN and detailed GPS data extended to 30 September only, it is not known whether ramming was needed for the eastbound transit of Region 2.

4.2.3 Region 3: Coronation Gulf

The LSSL required only four rams during the two voyage segments for which data from Region 3 are available. The four rams were conducted on 7 August in an area of less than 1/10th concentration of old ice. Peak global forces for the four rams ranged from 4.0 to 7.4MN for ship speeds of 8.5 to 15.6kt. The ramming speed of 15.6kt is the highest impact speed that was used to ram any of the floes during the three years of Arctic voyages.

The time-series trace in Figure 13 shows that the four rams were conducted over a 30 minute period as the ship steamed 3.7km through Coronation Gulf. The ship ramming track showed that Ram #1 and #2 were conducted 500m away from one another. Ram #1 took place at a speed of 8.5kt and produced a maximum force of 7.0MN (9939 s). A speed of 15.6kt was used for Ram #2 which produced a peak force of 7.4MN (10298 s). The ship steamed about 2.2km through the less than 1/10th concentration of old ice before conducting two more rams. Ram #3 took place at a speed of 11.3kt and caused a global force of 5.1MN (10871 s). Ram #4 was conducted just 700m away, when the ship impacted the ice at 12.5kt, producing a global force of 4.0MN. Images from the forward-looking camera were not available for these four ramming events, so it is not known whether the ship impacted various isolated floes or one massive floe during the 30 minutes that it took to steam the 3.7km distance.

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Figure 13 Global force record for highest ramming speed noted during three Arctic voyages

4.2.4 Region 4: Southern Beaufort Sea

The 26 rams that occurred in Region 4 all involved the same old ice floe, a portion of which is shown in the aerial photograph in Figure 14. The Ice Service Specialist (ISS) onboard the LSSL stated that this 11km diameter aggregate floe was the first ‘true’ multi-year floe that the ship had encountered since setting sail earlier that day (after the crew change) and that the immense floe was an anomaly because the concentration of ice around it was relatively loose (B. Molyneaux, personal communication). Although the surrounding ice may have been more benign, evidently the nearby pingo sites restricted the LSSL’s navigation options. The portion of the ice map that covered the location where the ship encountered this immense floe indicated ice concentrations of 1 to 3/10ths (green area) to 4 to 6/10ths (yellow area, see Figure 6-b). This confirms what the Commanding Officer relayed when he mentioned that the ice pack had drifted much further south in 2009 than in previous years (Captain M. Rothwell, personal communication).

To the untrained eye, this aggregate old ice floe may not appear to be formidable but the floe’s hummocked surface, embedded sediment and interconnected ponds reveal that the ice is very thick. In the author’s experience, the raised areas of ice in the portion of the floe noted by the arrow were likely more than 15 m thick. That estimate comes from detailed drill-hole thickness measurements made on similar floes in other areas of the Arctic, as noted in Johnston and Timco (2008).

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Figure 14 Old ice floe that impeded the ship’s progress in the southern Beaufort Sea

LSSL is circled; arrow shows a ponded multi-year floe that was likely upwards of 15m thick. This floe ice

provides justification for extending the boundaries of Zone 4, as suggested in Figure 1. (photo courtesy of B. Molyneaux, ISS CIS)

The 26 rams with the floe that was encountered on 8 August produced peak global impact forces of 4.4 to 26.4MN for ship impact speeds of 5.8 to 11.9kt. The highest impact force of the series occurred about mid-way through the series of rams (26.4MN, ram #11) when the ship rammed the ice at 10.1kt. The second highest force of the series occurred during the second to last ram, when the ship impacted the ice at 9.5kt (20.7MN, ram #25). On average, the peak global impact force of the 26 rams was 11.8MN and the average ramming speed was 9.7kt. Images from the forward-looking camera were not available for this period.

The LSSL also operated in Region 4 from mid-September to mid-October, where old ice concentrations in some areas were up to 4 to 6/10ths but it is not known whether ramming activity took place because MOTAN data and detailed GPS data were not available after 30 September. It should be noted, however, that two rams were conducted in Region 6 on the 25 September, only about 150km northwest of where the 8 August floe was encountered. Those two rams are included in Region 6, as discussed further below.

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Figure 15 Ridged floe that caused a 4.7MN force when rammed at 10.4kt in Region 5

(image courtesy of J. Hutchings) 4.2.5 Region 5: Arctic Basin

The LSSL operated in Region 5 at various times during August (Wk-2, Wk-3), September (Wk-1, Wk-2) and October (Wk-1). One ram occurred during that entire period. The ram that occurred on 22 August resulted from the ship impacting a ridge at a speed of 10.4kt, resulting in a peak global force of 4.7MN. Figure 14 shows the ridge that is expected to have caused the event. The ridge is evident just in front of the ship’s bow but it appears quite small from the perspective of the forward-looking camera (high on the mast). The 4.7MN force and the decrease in ship speed caused by the impact show that the ridge was more substantial than it looks in the image.

4.2.6 Region 6: Queen Elizabeth and Banks Islands

During the 2009 season, the LSSL operated in Region 6 for two weeks in August, two weeks in September and one week in

October. A total of 235 rams were conducted during the August-September timeframe (data are not available for October). Peak global forces for the 6 rams that occurred in mid-August ranged from 4.3 to 12.8MN. Global forces ranged from 3.2 to 17.4MN for the 227 rams that were conducted in late-August. The two rams that were required in late-September produced global forces of 6.4 and 11.2MN. The images in Figure 16 show the three ice features that were believed to have caused some of the highest ram-related forces in Region 6 during August and September. The images were selected because of their good visibility.

Most of the ramming activity in Region 6 took place as the LSSL traversed a ‘loop’ at the northernmost reaches of its 2009 voyage (Figure 9). From 27 to 30 August, the LSSL struggled through a 100km wide and 240km long loop. Five engines were brought online on for twelve to fourteen hours on 29 and 30 August, and for five hours on 30 August (Captain S. Julien, personal communication).

A total of 52 rams was conducted on the west side of the loop and 122 rams on the east side of the loop. Given the difference in the number of rams conducted along the two segments, one might expect ice conditions on the east side of the loop to have been more severe than the west side, even though the two segments were just 100km apart. In this case, the increased number of rams required while transiting ice on the eastern side of the loop may not indicate that the ice was more severe: decreased visibility would have made navigating through the ice more difficult since the weaker areas of ice and/or open water leads could not be exploited if they were difficult

Monitoring global ice impact forces on the CCGS Louis S. St-Laurent : interim report

Archives des publications du CNRC

Monitoring Global Ice Impact Forces on the

CCGS

Louis S. St-Laurent: Interim Report

M. Johnston

Technical Report, CHC-TR-086

March 2012

Monitoring Global Ice Impact Forces on the

CCGS

Louis S. St-Laurent: Interim Report

Table of Contents

List of Figures

List of Tables

Monitoring Global Ice Impact Forces on the

CCGS

Louis S. St-Laurent: Interim Report

1.0 Introduction

2.0 Relevance to Shipping Regulations

3.0 Sources of Data used for this Report

4.0 Voyages of CCGS Louis S. St-Laurent

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