Publisher’s version / Version de l'éditeur:
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la
première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez
pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the
first page of the publication for their contact information.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site
LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
The Seventh International Conference on Port and Ocean Engineering under
Arctic Conditions. POAC 83, 2, pp. 875-887, 1983
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
https://nrc-publications.canada.ca/eng/copyright
NRC Publications Archive Record / Notice des Archives des publications du CNRC :
https://nrc-publications.canada.ca/eng/view/object/?id=c38b446c-8d3d-49ba-9e57-5e0dbb0e054f
https://publications-cnrc.canada.ca/fra/voir/objet/?id=c38b446c-8d3d-49ba-9e57-5e0dbb0e054f
NRC Publications Archive
Archives des publications du CNRC
This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. /
La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version
acceptée du manuscrit ou la version de l’éditeur.
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
Ice behaviour around a small Arctic island
TH1
N21d
National Research
Conseil national
no*
Council Canada
c .
2
de
recherches Canada
BLDG
ICE REHAVIOUR AROUND A SMALL ARCTIC ISLAND
by
R. Frederking, T. Sanderson, E. Wessels
and
M.
lnoue
Appeared
in
VTT Symposium
28
The Seventh International Conference o n Port and
Ocean Engineering under Arctic Conditions
Helsinki, Finland, 5
-
9 April, 1983
Volume
2,
p. 875
-
887
Reprinted with permission
Technical Research Centre o f Finland (VTT)
,.
p 2 -
i-!
I
DB R Paper No. 1
149
i 3 : T , .
,. - -
. ,-
.
, . t - - * - 1
Division o f Building Research
?.,-,.i,,
I;;-:- I-;l,,b;, T J . - -
>.--.-.-,
I-,R. Frederking, D i v i s i o n of B u i l d i n g Research, N a t i o n a l Research Council of Canada, Ottawa. Canada KIA 0R6.
T. Sanderson, BP Petroleum Development (Overseas) Ltd. London ECZY 9BU. England.
E . Wessels, Hamburgische Schiffbau-Versuchsanstalt (HSVA),
Hamburg. West Germany.
M. Inoue, Nippon Kokan K.K., Japan. ( V i s i t i n g s c i e n t i s t a t DBR, NRC
.
)ICE BEHAVIOUR AROUND A SMALL ARCTIC ISLAND
A b s t r a c t
Adams I s l a n d , 200 m i n diameter and about 3 km o f f s h o r e i n L a n c a s t e r Sound, has been e s t a b l i s h e d a s a s i t e f o r s t u d y i n g i c e i n t e r a c t i o n processes. P r e l i m i n a r y s u r v e y s of i c e and
environmental c o n d i t i o n s o v e r t h e w i n t e r 1981/82 shoved i c e f e a t u r e s r e f l e c t i n g a short-term p i l e - u p a s w e l l a s long-term t h r u s t on t h e i s l a n d . A s s o c i a t e d i c e p r e s s u r e s were i n t h e range 40-400 Wa. Information on f i r s t - y e a r i c e c o v e r , i c e b e r g s and m u l t i - y e a r f l o e s was a l s o c o l l e c t e d .
1. INTRODUCTION
A s m a l l i s l a n d can be taken a s r e p r e s e n t a t i v e of a man-made o f f s h o r e s t r u c t u r e . Observations of i c e i n t e r a c t i o n s w i t h t h e i s l a n d a r e r e l e v a n t t o p r e d i c t i n g i c e f o r c e s on s t r u c t u r e s . provided t h e r e a r e s u i t a b l e i c e c o n d i t i o n s and movements. T h i s approach was used i n an i n v e s t i g a t i o n of impact of l a r g e multi- y e a r f l o e s on Hans I s l a n d / 6 / . S i m i l a r s t u d i e s have been made of f i r s t - y e a r s e a i c e rubble formations a t Fairway Rock / 5 / . Adams I s l a n d , about 200 m i n diameter, i s l o c a t e d a t t h e i n t e r s e c t i o n of L a n c a s t e r Sound and Navy Board I n l e t i n t h e Canadian A r c t i c . I c e c o n d i t i o n s i n t h e a r e a i n c l u d e l e v e l f i r s t - y e a r s e a i c e , p r e s s u r e r i d g e s , multi-year i c e , pack i c e and i c e b e r g s . Both
dynamic and l a n d - f a s t i c e c o n d i t i o n s p r e v a i l o v e r t h e c o u r s e of t h e w i n t e r .
A j o i n t p r o j e c t , t o extend over t h r e e w i n t e r s e a s o n s , w i t h p a r t i c i p a n t s from s e v e r a l c o u n t r i e s , was i n i t i a t e d t o o b s e r v e and measure i c e i n t e r a c t i o n p r o c e s s e s and environmental d r i v i n g f o r c e s around Adams I s l a n d i n o r d e r t o c h a r a c t e r i z e t h e p r o c e s s e s and develcp a n a l y t i c a l models f o r p r e d i c t i n g i c e f o r c e s . Over t h e w i n t e r 1981182, p e r i o d i c s i t e v i s i t s , i n c l u d i n g s e v e r a l by a c o n t r a c t o r and a 2-week major f i e l d v i s i t i n March, were made t o survey i c e and environmental c o n d i t i o n s . A more e x t e n s i v e p r e s e n t a t i o n of t h e s e r e s u l t s a p p e a r s elsewhere 131.
2. SITE DESCRIPTION
The a r e a of i n v e s t i g a t i o n i s a t t h e i n t e r s e c t i o n of L a n c a s t e r Sound and Navy Board I n l e t (Fig. 1). L a n c a s t e r Sound, t h e
F I G U R E 1
e a s t e r n e n t r a n c e t o t h e Northwest Passage, extends t o t h e west from B a f f i n Bay i n t o t h e i s l a n d s of t h e Canadian Arctic. I c e moves g e n e r a l l y eastward through L a n c a s t e r Sound, under t h e a c t i o n of wind and c u r r e n t . Navy Board I n l e t i s a f i o r d - l i k e f e a t u r e which c o n n e c t s through E c l i p s e Sound and Pond I n l e t t o B a f f i n Bay. Water d e p t h i n L a n c a s t e r Sound reaches 800 m, and
400 m i n Navy Board I n l e t . A s i l l a t t h e i r i n t e r s e c t i o n does n o t
exceed 200 m i n d e p t h and f o r t h e most p a r t is l e s s t h a n 100 m deep. The t i d a l range i s about 1.5 m.
Adams I s l a n d i s s i t u a t e d about 3 km o f f s h o r e from t h e Borden P e n i n s u l a ( F i g . 1 i n s e r t ) . Borden S t a t i o n , w i t h accomodatioa b u i l d i n g s and a 300 m a i r - s t r i p , provided a base f o r o p e r a t i o n s i n t h e a r e a . A d e t a i l e d map of t h e i s l a n d and l o c a l bathymetry a r e shown i n F i g . 2 . The i s l a n d is rocky, w i t h s t e e p c l i f f s on
0 S H O R I - T E R M I C E M O V E M E N T L l A R K E R S L O h G - I C R M ICf M O V C h l E N T S I I R V E Y P O L E S Fig. 2 Adams I s l a n d s h a r i n g p r o f i l e d f e a t u r e s , i c e movements and bathymetry ( w a t e r d e p t h i n m)
-
I l O l i E h l L N I S C A L E m i > 0 I 9 2 I O C h ! A D S C A L E mt h e n o r t h s i d e . Maxinum e l e v a t i o n ( 2 0 m) i s on t h e n o r t h e r n s i d e , w i t h g r a d u a l s l o p e s t o t h e e a s t , s o u t h and west. The s o u t h s h o r e i s a l s o n e a r v e r t i c a l , w i t h a n escarpment a b o u t 4 m high. The beaches a r e rocky and r e l a t i v e l y s t e e p
1 7 1 .
There i s no p o s s i b i l i t y of l a n d i n g even a s m a l l b o a t on t h e i s l a n d , e x c e p t on a mobile s p i t on t h e southwest c o r n e r . A s can be s e e n i n Pig. 2 , t h e s l o p e of t h e s e a bottom i s g r a d u a l t o t h e n o r t h and west. The s t e e p e s t submarine s l o p e is t o t h e s o u t h e a s t . The s e a bottom i s very rocby.For a normal s e a s o n , i c e f i r s t forms i n t h e middle of Navy Board I n l e t i n October. T h i s i c e becomes l a n d - f a s t and p r o g r e s s e s up t h e i n l e t , r e a c h i n g L a n c a s t e r Sound i n December. The i s l a n d i s g e n e r a l l y a t t h e boundary between l e v e l and r i d g e d ice. Shear and p r e s s u r e r i d g e s form a zone of r i d g e d i c e which becomes land- f a s t i n mid-winter t o about 2 Ian n o r t h o f t h e i s l a n d . During t h e open water s e a s o n , multi-year i c e from t h e A r c t i c Archipelago moves through L a n c a s t e r Sound t o be d i s c h a r g e d i n t o B a f f i n Bay. S i m i l a r l y , i c e b e r g s from t h e g l a c i e r s of Greenland and E l l e s m e r e I s l a n d c i r c u l a t e i n t h e Sound. Some of t h e s e b e r g s p a s s i n t o Navy Board I n l e t and a r e f r o z e n i n t o t h e i c e cover w h i l e o t h e r s ground on t h e s i l l a t t h e e n t r a n c e t o t h e i n l e t . T y p i c a l l y t h e r e can be 5 t o 10 l a r g e i c e b e r g s w i t h i n 10 km of Adam I s l a n d . Multi-year i c e i s a l s o f r o z e n i n t o t h e i c e c o v e r and may r e a c h - coverages of 1 t o 5%. The pack i n L a n c a s t e r Sound i s g e n e r a l l y dynamic throughout t h e e n t i r e w i n t e r a l t h o u g h on o c c a s i o n i t h a s been r e p o r t e d a s completely l a n d - f a s t and s t a t i c / I / .
3. ICE PROFILES
I c e i n t e r a c t i o n s i n t h e immediate v i c i n i t y of Adams I s l a n d were c h a r a c t e r i z e d by measuring v e r t i c a l p r o f i l e s a l o n g s e v e r a l l i n e s extending o u t from t h e i s l a n d . The r e s u l t s of two r e p r e s e n t a t i v e l i n e s , one t o t h e southwest b e l i e v e d t o r e p r e s e n t a l o n g term t h r u s t ( b u c k l e ) f e a t u r e , and t h e o t h e r t o t h e s o u t h e a s t
-
879-
P i g s . 3 a n d 4 r e s p e c t i v e l y . The p r o f i l e s w e r e c o n s t r u c t e d from measurements of s u r f a c e e l e v a t i o n , i c e t h i c k n e s s , s n o v d e p t h and w a t e r d e p t h a t 4 m i n t e r v a l s . T h e s e measurements were made d u r i n g t h e March f i e l d v i s i t .
3.1 Long t e r m t h r u s t ( b u c k l e ) f e a t u r e
The p r o f i l e i l l u s t r a t e d i n Fig. 3 i s t y p i c a l of a f e a t u r e which e x t e n d e d f o r a b o u t 150 m a l o n g t h e s o u t h w e s t s i d e of t h e i s l a n d , r o u g h l y p a r a l l e l t o t h e s h o r e . The i c e t h i c k n e s s i n t h i s f e a t u r e (2-3 m) i s g r e a t e r t h a n t h e a d j a c e n t l e v e l i c e (1.3 m). T h i s i s -f 5 T I D A L
-
-
.I M E A S U R E D P O I N T S / / 5 S N O W WXY R O C K - - l a F I G U R E 3 P R O F I L E O F S O U I H W E S T I C E F E A T U R E A O A M S I S L A N D M A R C H 1 9 8 2 most l i k e l y due t o w a t e r f l o o d i n g o n t o t h e s u r f a c e a t h i g h t i d e and s u b s e q u e n t l y f r e e z i n g . T i d a l f l o o d i n g was o b s e r v e d d u r i n g t h e c o u r s e of t h e two-week f i e l d v i s i t . T i d a l c r a c k s were a l s o n o t e d and s e e n t o change, some becoming i n o p e r a t i v e and new o n e s f o r m i n g . A s i m i l a r t i d a l - r e l a t e d t h i c k e n e d i c e zone h a s been o b s e r v e d i n S t r a t h c o n a Sound a r o u n d a wharf 1 2 1 .The n e a r - v e r t i c a l i c e f e a t u r e a t 2 0 m was produced by a
p r o g r e s s i v e t i l t i n g up of t h e i c e c o v e r . T h i s r o t a t i o n i s shown by t h e c u r v e d a r r o w i n F i g . 3. F u r t h e r e v i d e n c e was a s e t of snowmobile t r a c k s , c l e a r l y v i s i b l e on t h i s n e a r v e r t i c a l s u r f a c e ; t h e y had been made d u r i n g a February r e c o n n a i s s a n c e t o t h e
i s l a n d . At some p o s i t i o n s a l o n g t h e f e a t u r e t h e t i l t - u p was n o t a s g r e a t and i n o t h e r c a s e s t h e r o t a t i o n was more t h a n 90'. As y e t t h e r e i s no d e f i n i t e e x p l a n a t i o n f o r t h i s t i l t i n g . It i s
most l i k e l y due t o t h e combined e f f e c t s of b u c k l i n g , r e s u l t i n g from h o r i z o n t a l movement of t h e i c e c o v e r towards t h e i s l a n d , and t i d a l c y c l i n g .
3.2 Pile-up f e a t u r e
The p r o f i l e of t h e p i l e - u p on t h e s o u t h e a s t s i d e of t h e i s l a n d ( F i g . 4 ) i s r e p r e s e n t a t i v e of t h i s f e a t u r e , which e x t e n d e d f o r a l e n g t h of a l m o s t 50 m a l o n g t h e s h o r e . A s i g n i f i c a n t p a r t of t h e p i l e - u p i s above t h e mean s e a l e v e l and i t e x t e n d s a b o u t 10 m
n i E A S U R E D P O I N T S
I
H A R D I C E ' S O F i I C E = G A P . S H O W I N G S I Z I - G A P . 5 c m O R L E S S ,"', S N O W ;YA-+ R 0 C K 11 A C T I V E C R A C K---
- z 0 : P O S I T I O N , m < > P O S I T I O N . n F I G U R E C P R O F I L E OF P I L E - U P O Y S O U T H L A S T S I D E OF A O A M S I S L n ' r D h l A R C H 1982 i n l a n d . V i s u a l l y t h e r e appeared t o be b o t h f i r s t - y e a r and m u l t i - y e a r i c e i n t h e p i l e - u p . The d e s i g n a t i o n s of " h a r d " and " s o f t " i c e a r e q u a l i t a t i v e and r e l a t e d t o t h e e a s e of d r i l l i n g t h r o u g h t h e p i l e - u p . T h e h a r d ' ' i c e o u t t o t h e 1 2 m p o s i t i o n wasextremely hard, probably due t o t h e low temperature of t h e i c e and t h e presence of m u l t i y e a r i c e fragments. Some i c e b l o c k s on t h e s u r f a c e of t h e pile-up measured from 0.3 t o 0.65 m t h i c k . w i t h an average of 0.45 m. The l e n g t h s and widths were from 3 t o
4 t i m e s t h e t h i c k n e s s . Based on t h e l e n g t h s of v o i d s encountered w h i l e d r i l l i n g through t h e p i l e - u p (-lo%), a volume p o r o s i t y v a l u e of 0.3 was e s t a b l i s h e d . The pile-up probably occurred i n December, s h o r t l y b e f o r e f r e e z e - u p , when f i r s t - y e a r i c e 0.3 t o
0.4 m t h i c k was present.
The s h o r e i n t h e a r e a was q u i t e rocky, w i t h a s l o p e of about 1:4
( F i g . 4), s i m i l a r t o t h e s l o p e of t h e s e a bottom i n Fig. 2. The s l o p e of t h e pile-up between 0 and t h e 5 m p o s i t i o n was about
1:l. between t h e 5 m and 13 m p o s i t i o n s , about 1:4. and between
13 m and 17 m. about 1:l. Taking t h e p o r o s i t y v a l u e of 0.3. a n
80 m movement of 0.45 m-thick i c e would b e r e q u i r e d t o form t h e observed f e a t u r e . From t h e c r o s s - s e c t i o n a l shape of t h e pile-up,
i t i s p o s s i b l e t h a t a n e q u i l a t e r a l - t r i a n g u l a r s h a p e d p i l e - u p of s l o p e about 1:l formed a t t h e p o i n t of maximum shoreward i n t r u s i o n , reaching a lid t i n g h e i g h t . With c o n t i n u i n g i c e movement, t h e pile-up would c o n t i n u e t o grow t o seaward u n t i l t h e i c e movement ceased. A t t h e p o i n t of maxi~rmm landward i c e i n t r u s i o n t h e r e was no obvious s h o r e o b s t r u c t i o n which would have l i m i t e d i c e movement.
Kovacs and Sodhi
151
have proposed a n a p p r o a c h - f o r c a l c u l a t i n gt h e f o r c e r e q u i r e d t o add g r a v i t a t i o n a l p o t e n t i a l energy t o a s h o r e pile-up. The r e s u l t i n g e q u a t i o n h a s t h e form
where F = f o r c e per u n i t w i d t h
a = a f a c t o r which depends on t h e shape of t h e pile-up and t h e s l o p e of t h e s h o r e ( v a l u e i n range 1 t o 2 )
pi = d e n s i t y of i c e
Hs = h e i g h t of i c e p i l e - u p t = i c e t h i c k n e s s .
For t h e geometry of t h e p i l e - u p observed (He = 5 m, t = 0.45 m. a = 1.5). t h e f o r c e p e r u n i t w i d t h r e q u i r e d t o b u i l d t h e p i l e - u p was c a l c u l a t e d t o be 15 kN/m o r , i n terms of i c e p r e s s u r e f o r t h e g i v e n i c e t h i c k n e s s , 35 kPa. That d o e s n o t i n c l u d e f r i c t i o n a l e f f e c t s s o t h e l o a d s e s t i m a t e d a r e a l w e r bound. An upper bound can be determined by e s t i m a t i n g t h e r e s i s t a n c e t o s l i d i n g o f f e r e d by t h e rubble. The s l i d i n g r e s i s t a n c e p e r u n i t a r e a i s
where
u
= c o e f f i c i e n t of s t a t i c f r i c t i o n between t h e i c e and s h o r eo n = v e r t i c a l p r e s s u r e on s h o r e .
The v e r t i c a l p r e s s u r e can b e , c a l c u l a t e d from simple buoyancy and g r a v i t y c o n s i d e r a t i o n s ,
where H = s a i l h e i g h t , above w a t e r l i n e o r s h o r e
-
k e e l d e p t h , below w a t e r l i n epi, 0,- d e n s i t i e s of i c e and water r e s p e c t i v e l y cs. ck = p o r o s i t i e s of s a i l and k e e l r e s p e c t i v e l y .
The value of t h e v e r t i c a l p r e s s u r e , o n , w i l l vary w i t h p o s i t i o n r e l a t i v e t o s h o r e . V e r t i c a l p r e s s u r e s c a l c u l a t e d a t t h e d r i l l p r o f i l e l o c a t i o n s o u t t o t h e 15 m p o s i t i o n ( w i t h cs = 0 . 3 . ck
-
0 ) a r e p l o t t e d on Fig. 4 . The a v e r a g e v e r t i c a l p r e s s u r e was 18 Wa. Using t h i s v a l u e i n e q u a t i o n ( 2 ) , w i t h a f r i c t i o n c o e f f i c i e n t of 0 . 7 , y i e l d e d a s l i d i n g r e s i s t a n c e of 196 kN/m o r a n e q u i v a l e n t p r e s s u r e of 4 3 0 kPa i n 6.45 m-thick i c e . The two c a s e s e v a l u a t e d e s t a b l i s h t h e upper and lower bounds f o r t h e f o r c e r e q u i r e d t o develop t h e pile-up.4. ICE UOVEIIENTS
4.1 S h o r t - t e r m movements
An a r r a y of s e v e n markers was e s t a b l i s h e d o n t h e i c e a t d i s t a n c e s o f 200 t o 400 m from t h e i s l a n d ( s e e Pig.2 f o r a c t u a l l o c a t i o n s ) . The p o s i t i o n s of t h e markers were s q r v e y e d u s i n g t h e o d o l i t e i n t e r s e c t i o n from a b a s e network of t h r e e f i x e d s t a t i o n s on t h e i s l a n d . The p r e c i s i o n of a p o s i t i o n f i x waa e s t i m a t e d a s 25 mm
i n t h e t a n g e n t i a l d i r e c t i o n a n d 100 mm i n t h e r a d i a l d i r e c t i o n . The measurements t o marker "S" were u n r e l i a b l e due t o t h e s m a l l a n g l e of i n t e r s e c t i o n . T h r e e c o m p l e t e s u r v e y s were made, on March 14, 17 and 20. The r e s u l t s a r e p r e s e n t e d i n Pig. 5.
MAR 17-20 ICE MOVEMENTS c - - - 4 MARCH 17-20 I X A L I . s A 0 510 I000 M A ? SCALE.
-
F i g . 5 S h o r t t e r m i c e movements, Adams I s l a n d . Harch 14-20 1982.During t h e f i r s t time i n t e r v a l , March 14-17, t h e r e were h i g h winds from t h e e a s t and s o u t h , w i t h a maxinum v e l o c i t y of 21 m s - l . These winds r e s u l t e d i n t h e i c e movements shown a s s o l i d v e c t o r s i n Fig. 5 and a l s o g a v e r i s e t o a n open f r a c t u r e t o t h e n o r t h of marker "E". The r o o t mean s q u a r e wind v e c t o r is
p l o t t e d f o r comparison w i t h t h e i c e movement v e c t o r s . The movements a r e a b o u t a m e t r e , w e l l above t h e r e s o l u t i o n of t h e measurements. The d i r e c t i o n s of movement a r e n o t a s might be e x p e c t e d . Although markers t o t h e n o r t h and west of Adams I s l a n d
shov a roughly c o h e r e n t movement t o t h e n o r t h , markers "S" and
"SE" show movement t o t h e s o u t h , a g a i n s t t h e predominant wlnd
d i r e c t i o n . T h i s v e l o c i t y f i e l d i s n o t c o n s i s t e n t w i t h a s i m p l e model i n which a uniform s l a b of i c e i s d r i v e n a g a i n s t a n o b s t a c l e and c r e e p s s t e a d i l y around i t . I n such a model, motion cannot occur c o n t r a r y t o t h e d r i v i n g f o r c e ; i c e immediately upwind of t h e i s l a n d s h o u l d be moving t c u a r d s i t and undergoing compressive s t r a i n . The v e l o c i t y f i e l d observed shows v e r y l i t t l e e v i d e n c e of compressive s t r a i n . I t i s l i k e l y t h a t new o r e x i s t i n g f r a c t u r e s a r e f a c i l i t a t i n g movement and t h a t l a r g e a r e a s of i c e a r e moving a s blocks, undergoing t r a n s l a t i o n s and
r o t a t i o n s under t h e f o r c e s e x e r t e d by wind d r a g and t h e r e a c t i o n of t h e i s l a n d . A g r o s s block r o t a t i o n may l e a d t o movements c o n t r a r y t o t h e d r i v i n g f o r c e .
During t h e second time i n t e r v a l , March 17-20, winds were from t h e west w i t h a maximum v e l o c i t y of 9 m s - l . These movements a r e shown by broken v e c t o r s i n Fig. 5. They a r e c o n s i d e r a b l y s m a l l e r t h a n t h o s e of t h e p r e v i o u s p e r i o d and a r e only b a r e l y
s i g n i f i c a n t . Again, movements shown a r e broadly d i v e r g e n t from t h e i s l a n d and n o t c o n s i s t e n t w i t h uniform c r e e p around i t .
4.2 Long-term movements
A d d i t i o n a l i c e movement i n f o r m a t i o n i s a v a i l a b l e f o r t h e n e a r - i s l a n d i n t e r a c t i o n zone t o t h e w e s t of Adams I s l a n d . A s e r i e s of survey p o l e s was i n s t a l l e d i n t h e i c e d u r i n g February, and measurements were made of d i s t a n c e s between them and of d i s t a n c e s from f i x e d p o i n t s on t h e i s l a n d . See Fig. 2 f o r l o c a t i o n s of t h e s e poles. The survey l i n e was i n i t i a l l y l i n e d up v i s u a l l y .
The l i n e was remeasured i n March and June. The changes i n measured d i s t a n c e from t h e i s l a n d p r o v i d e r a d i a l movement i n f o r m a t i o n , and t h e d i s t a n c e moved o u t of l i n e p r o v i d e s t a n g e n t i a l movement i n f o r r a t i o n . Also, changes i n d i s t a n c e between on-ice survey p o l e s p r o v i d e s t r a i n i n f o r m a t i o n . The movement v e c t o r s of t h e two p o l e s a r e i n d i c a t e d by arrows i n
Fig. 2. Movements were of t h e o r d e r of 1 t o 2 m p e r month and i n
a n e a s t e r l y d i r e c t i o n (towards t h e i s l a n d ) . Most of t h i s movement i s accommodated i n t h e t h r u s t ( b u c k l e ) f e a t u r e . The f i r s t - y e a r i c e does n o t appear t o be moving towards t h e i s l a n d by simple compression c r e e p ; i n s t e a d i t i s f a i l i n g i n bending and moving a s a block i n t o t h e f a i l u r e zone. From t h e movement v e c t o r s , average compressive s t r a i n s between t h e two p o l e s of
3.3 x and 4.5 x were determined f o r t h e February-March and March-June p e r i o d s , r e s p e c t i v e l y . The corresponding average s t r a i n r a t e s would be s-l and 5 x 10-10 s-1. T h i s compares reasonably w e l l w i t h a v e r a g e s t r a i n r a t e of 10-lo s-I e s t i m a t e d f o r t h e f i r s t - y e a r i c e cover on S t r a t h c o n a Sound 121. Assuming a n average i c e t e m p e r a t u r e of -lO°C and s t e a d y s t a t e c r e e p
/ & I ,
t h e u n i a x i a l compression s t r e s s e s r e q u i r e d t o produce s t r a i n r a t e s of 10-9 s-1 and 5 x 10-10 6-1 a r e 180 and 140 kPa,
r e s p e c t i v e l y . T h i s method of e s t i m a t i o n y i e l d s a n average (lower bound v a l u e ) . Peak s t r e s s would c e r t a i n l y be higher.
5. ICE PROPERTIES
Extensive measurements wete made of t h e p r o p e r t i e s of t h e v a r i o u s i c e types found around Adam I s l a n d . Because of space
l i m i t a t i o n s , only s e l e c t e d r e s u l t s w i l l be d i s c u s s e d h e r e . Almost 30 measurements of t h i c k n e s s , sncw d e p t h and f r e e b o a r d i n a 40 by 80 m a r e a of l e v e l f i r s t - y e a r i c e a d j a c e n t t o t h e i s l a n d were made i n mid-March. The mean and s t a n d a r d d e v i a t i o n of d e p t h was 0.10 2 0.09 m and f r e e b o a r d , 0.13 2 0.09 m. This
demonstrates t h e l a r g e s p a t i a l v a r i a b i l i t y i n snaw d e p t h and f r e e b o a r d , which i s common f o r f i r s t - y e a r s e a i c e . Temperature measurements i n l e v e l f i r s t - y e a r i c e y i e l d e d l i n e a r g r a d i e n t s with mean i c e cover t e m p e r a t u r e s of -10 t o - 1 2 ° C . I n one of t h e flooded i c e zones ( a b o u t 1.8 m t h i c k ) a d j a c e n t t o t h e t h r u s t f e a t u r e , i c e t e m p e r a t u r e i n c r e a s e d from -17'C a t t h e s u r f a c e t o
-5°C a t 0.3 m d e p t h and remained c o n s t a n t a t t h i s temperature t o the bottom s u r f a c e . Such high i c e t e m p e r a t u r e s would be
c o n s i s t e n t w i t h a n e a s i l y d e f o r r a a b l e i c e c o v e r , as e v i d e n c e d by t h e t i l t e d - u p f e a t u r e i n Fig. 3.
A number of m u l t i - y e a r f l o e s were f r o z e n i n t o t h e i c e c o v e r i m m e d i a t e l y a d j a c e n t t o Adam I s l a n d ; t h e i c e movement markers
"NU" and "S" were l o c a t e d on m u l t i - y e a r f l o e s . The d i m e n s i o n s o f s e v e r a l f l o e s were measured. They a v e r a g e d 7 m t h i c k and a b o u t 40 m i n d i a m e t e r , w i t h a n e s t i m a t e d w e i g h t of 10 t o n n e s . The f l o e s were n o t grounded and t h e r e was n o e v i d e n c e t h a t t h e y were moving w i t h r e s p e c t t o t h e s u r r o u n d i n g i c e . It was a p p a r e n t , h w e v e r , t h a t i n t h e l a t t e r s t a g e s of f r e e z e - u p , f i r s t - y e a r i c e had f a i l e d a g a i n s t them, b u i l d i n g up s m a l l r u b b l e a c c u m u l a t i o n s which, i n some c a s e s , e n c r o a c h e d on t h e t o p s u r f a c e of t h e f l o e .
I n March d e t a i l e d s u r v e y s were made of two i c e b e r g s l o c a t e d i n t h e e n t r a n c e t o Navy Baard I n l e t . T h e i r a b o v e - w a t e r d i m e n s i o n s were e s t i m a t e d from a c o m b i n a t i o n of r a d a r f i x e s and p h o t o g r a p h s . A v i s i t t o t h e i c e b e r g s e s t a b l i s h e d t h a t t h e y w e r e grounded, i . e . , t i d a l h i n g e s were o b s e r v e d i n t h e i c e c o v e r a r o u n d them. Water d e p t h measurements were made a d j a c e n t t o e a c h berg. I n o n e c a s e , w a t e r d e p t h was 118 m and i n t h e o t h e r i t exceeded 139 m. The e s t i m a t e d mass of e a c h b e r g i s 2 x l o 6 t o n n e s .
A t i m e l a p s e camera s y s t e m - b a s e d on a Super 8 movie camera was u s e d t o r e c o r d t h e e v o l u t i o n of i c e c o n d i t i o n s a s w e l l a s t h e p r o g r e s s i o n of break-up. The camera was p l a c e d i n a n i n s u l a t e d box, which a l s o c o n t a i n e d a h e a t e r a n d a t h e r m o s t a t t o c o n t r o l t h e t e m p e r a t u r e a t -lO°C ('2°C) t o e n s u r e s u f f i c i e n t f i l m f l e x i b i l i t y . A t i m e r a c t i v a t e d t h e camera t o t a k e o n e frame e v e r y 30 m i n u t e s , t h u s a l l o w i n g one f i l m c a s s e t t e t o l a s t o v e r two months. A f u l l y charged 230 amp-hour l e a d - a c i d b a t t e r y s u c c e s s f u l l y o p e r a t e d t h e camera s y s t e m f o r o v e r two months a t a m b i e n t t e m p e r a t u r e of a b o u t -30°C. A l t o g e t h e r e i g h t months of f i l m r e c o r d was o b t a i n e d between two cameras.
The l o g i s t i c s u p p o r t provided by P o l a r C o n t i n e n t a l S h e l f P r o j e c t i s g r e a t l y a p p r e c i a t e d , a s i s t h e u s e of t h e f a c i l i t i e s a t Borden S t a t i o n , owned by t h e Canadian Dept. of F i s h e r i e s and Oceans. T e c h n i c a l s u p p o r t was p r o v i d e d by t h e A r c t i c Research
~ s t a b l i s h m e n t of Pond I n l e t . F i n a n c i a l s u p p o r t of t h e German
U i n i s t r y of R e s o u r c e s and Technology made p o s s i b l e t h e p a r t i c i p a t i o n of HSVA i n t h e p r o j e c t .
REFERENCES
I . DEY. Balaram B., Shipping r o u t e s , i c e c o v e r and year-round n a v i g a t i o n i n t h e Canadian A r c t i c . P o l a r Record, Vol. 20, No. 129, 1981, pp. 549-559.
2. FREDERKING. R., I c e a c t i o n on N a n i s i v i k Wharf, S t r a t h c o n a
Sound, N.W.T. Winter 1978-79. Canadian G e o t e c h n i c a l
J o u r n a l , Vol. 7, No. 3, September 1980, pp. 558-563.
3. FREDERKING, R., INOUE, M., SANDERSW, T., and WESSELS, E.,
Adams I s l a n d P r o j e c t
-
Data R e p o r t Winter 1981-82. TO be p u b l i s h e d a s NRC r e p o r t , 1983.4. GOLD, L.W., A c t i v a t i o n energy f o r c r e e p of columnar-grained i c e . ( I n Whalley, E. e t a l . . eds. P h y s i c s and Chemistry of i c e : p a p e r s p r e s e n t e d a t t h e Symposium on t h e P h y s i c s and Chemistry of I c e , h e l d i n Ottawa, Canada,
14-18 August 1972.) Royal S o c i e t y of Canada, Ottawa,
1973, pp. 362-364.
5. KOVACS, A.. and SODHI, D.. Sea i c e p i l i n g a t Fairway Rock, B e r i n g S t r a i t , Alaska : O b s e r v a t i o n s and t h e o r e t i c a l a n a l y s i s . 6 t h I n t . Conf. on P o r t and Ocean Engineering u n d e r A r c t i c C o n d i t i o n s (POAC), Quebec 1981. Vol. 11, pp. 985-1000.
6. METGE, M.. DANIELEWZCZ, B., and HOARE. R., On measuring l a r g e
s c a l e i c e f o r c e s ; Hans I s l a n d 1980. 6 t h I n t . Conf. on P o r t and Ocean Engineering under A r c t i c C o n d i t i o n s (POAC), Quebec 1981. Vol. 11, pp. 629-642.
7 . STELTNER, H.A.R., D i r e c t o r , A r c t i c Research E s t a b l i s h m e n t . Pond I n l e t , N. W.T., p e r s o n a l comnunication 1982.
T h i s p u b l i c a t i o n i s b e i n g d i s t r i b u t e d by t h e Division of Building R e s e a r c h of t h e N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a . I t s h o u l d n o t b e r e p r o d u c e d i n whole o r i n p a r t without p e r m i s s i o n of t h e o r i g i n a l p u b l i s h e r . The Di- v i s i o n would b e g l a d t o b e of a s s i s t a n c e i n obtaining s u c h p e r m i s s i o n . P u b l i c a t i o n s of t h e D i v i s i o n m a y b e o b t a i n e d by m a i l - ing t h e a p p r o p r i a t e r e m i t t a n c e ( a Bank, E x p r e s s , o r P o s t O f f i c e M o n e y O r d e r , o r a cheque, m a d e p a y a b l e t o t h e R e c e i v e r G e n e r a l of Canada. c r e d i t NRC) t o t h e N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a , Ottawa. K I A OR6. S t a m p s a r e n o t a c c e p t a b l e . A l i s t of a l l p u b l i c a t i o n s of t h e Division i s a v a i l a b l e a n d m a y be o b t a i n e d f r o m the P u b l i c a t i o n s S e c t i o n , Division of Building R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a , O t t a w a .
