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Ice-dusting experiments to accelerate the melting of ice
KATIONAL mS%ARCH C O U K C I L
CANADA
D I V I S I O N O F R U I I l D I N G ,RESEARCH
I C % - D U S T I N G EX?ERIl'/J.EETS
T O ACZELBRATE !DIE 1: ZLTIYG O F I C F
I n t e r n a l i ? e 3 o r t No. 285 o f t h e
D i v i s i o n o f Zuildina i ? e s e a r c h
OTTA'11i
PREFACE
The s e v e r e w i n t e r s experienced over m o s t of Canada have some advantages and make p o s s i b l e a c t i v i t i e s which cannot be c a r r i e d on under l e s s s e v e r e c o n d i t i o n s . Many o t h e r a c t i v i t i e s c l o s e l y r e l a t e d t o o r dependent unon t h e weather may be s e r i o u s l y reduced o r i n t e r r u p t e d . O?P
of t h e s e , t h e n a v i g a t i o n of Canadian r i v e r s such a s t h e S t . Lawrence, i s of such g r e a t importance t h a t much thought h a s been given t o t h e v a r i o u s ways i n which t h e n a v l r a t i o n
season might be extended if o n l : ~ k y a few vrreeks.
These s e a r c h e s q u i t e n a t u r a l l y brought up t h e q u e s t i o n of a c c e l e r a t i n g s p r i n g break-un on l a k e s and
r i v e r s b y t h e use of d u s t t o i n c r e a s e t h e a b s o r ~ t i o n of s o l a r r a d i a t i o n by snow and i c e covers i n e a r l y s ~ r i n ~ ; . Thc
D i v i s i o n beaan a l i t e r a t u r e survev and a desk s t u c ? ~ o f t h e p o s s i b i l i t i e s , which lvas followed' b y l i m i t e d f i e l d ' e x o c r i n e n t s
i n 1952 a n d 1963, those i n t h e l a t t e r y e a r b e i n g c a r r i e d on w i t h t h e a s s i s t a n c e of t h e Department of Transport.
r e s u l t s of t h e s e s t u d i e s t o g e t h e r w i t h soqe f u r t h e r d i s c u s s i o n s of t h e 7roblern a r e nolv p r e s e n t e d .
The a u t 5 o r i s a r e s e a r c h o f f i c e r ;with t h e ;no~,v and I c e S e c t i o n i n t e r e s t e d i n hydrology an8 v a r i o u s rela-?cd t o p i c s i n v o l v i n z sno:'! and i c e .
TI.'?,. Hutchsn:l
ICE-DUSTING EXPERIMENTS
TO ACCELERATE THE ?JELTING OF ICE by
G. P. Williams
I n a p r e v i o u s s t u d y a n e v a l u a t i o n was made of t h e use of d u s t t o a c c e l e r a t e t h e m e l t i n g of i c e c o v e r s on l a k e s and r i v e r s i n Canada (1). I n t h a t s t u d y it was concluded t h a t under some c o n d i t i o n s i c e d u s t i n g w i l l
a c c e l e r a t e t h e m e l t i n g of i c e , b u t t h a t f i e l d t r i a l s were r e q u i r e d t o prove t h e f e a s i b i l i t y of t h e t e c h n i q u e .
Consequently, s m a l l - s c a l e i c e - d u s t i n g t r i a l s were under- t a k e n a t Ottawa i n t h e s p r i n g melt p e r i o d s of 1952 and 1963. Using t h e e x p e r i e n c e gained i n t h e s e t r i a l s , p a s t weather r e c o r d s a t s e v e r a l Canadian s t a t i o n s were examined t o e v a l u a t e t h e f e a s i b i l i t y of d u s t i n g . The r e s u l t s of t h i s a n a l y s i s and t h e c o n c l u s i o n s o b t a i n e d from t h e i c e - d u s t i n g t r i a l s a r e r e c o r d e d i n t h i s r e p o r t .
1962 DUSTING EXPERITilENTS
S e v e r a l d i f f e r e n t d u s t s were a p p l i e d t o snow and i c e cover t e s t s i t e s i n t h e Ottawa a r e a d u r i n g t h e s p r i n g m e l t p e r i o d of 1962. Table I i s a summary of t h e a r e a s covered, t h e t y p e of d u s t a p p l i e d and t h e a p p l i c a t i o n r a t e s . F i g u r e 1 summarizes t h e weather c o n d i t i o n s t h a t occurred d u r i n g t h e d u s t i n g t r i a l s and t h e d a t e s when t h e d u s t s were a p p l i e d . The e f f e c t i v e n e s s of t h e d u s t s i n a c c e l e r a t i n g melt r a t e s was a s s e s s e d by comparing t h e r a t e a t which t h e d u s t e d I c e o r snow c o v e r melted w i t h t h e melt r a t e of a d j a c e n t u n d i s t u r b e d snow o r i c e .
The a l b e d o o r r e f l e c t i v i t y of t h e t e s t s u r f a c e s was measured w i t h p o r t a b l e Kipp short-wave r a d i o m e t e r s
mounted on a s u r v e y o r ' s t r i p o d , and a p o r t a b l e p o t e n t i o m e t e r r e c o r d e r . I n a d d i t i o n , t h e a l b e d o a t one s i t e ( t h e undusted snoy c o v e r ) was observed c o n t i n u o u s l y w i t h Eppley s h o r t - wave r a d i o m e t e r s . F i g u r e 2 ( a ) i s a view of t h e Kipp
r a d i o m e t e r s measuring t h e a l b e d o of a d u s t e d snow s u r f a c e which was covered w i t h a new s n o w f a l l . The Eppley
Snow Dus t i n g Te s t s
A t t h e snow t e s t s i t e f i n e - p e l l e t c a r b o n b l a c k was a p p l i e d on 7 March a t t h e r a t e of 200 gmjnetre and 400 gmjmetre t o two t e s t p l o t s , e a c h
9
s q u a r e m e t r e s .V i t h i n a n h o u r of a p p l i c a t i o n t h e c a r b o n p e l l e t s , a b s o r b i n g h e a t from t h e s u n , had melted t h e i r way a b o u t 2 t o
3
i n .i n t o t h e snow pack.
' h e n t h e d u s t was f i r s t a p p l i e d , t h e a l b e d o of t h e d u s t e d s u r f a c e was below 15 p e r c e n t , compared t o a n a l b e d o of 50 t o 6 0 p e r c e n t f o r t h e n a t u r a l snow c o v e r . A f t e r t h e p e l l e t s had p e n e t r a t e d i n t o t h e snow c o v e r , t h e s u r f a c e became " g r e y - l i k e t 1 i n c o l o u r w i t h a r e l a t i v e l y low a l b e d o of 1 5 t o 20 p e r c e n t . The e x c e s s m e l t - w a t e r produced a t t h e d u s t e d s u r f a c e d r a i n e d i n t o t h e snow c o v e r and c o l l e c t e d on t h e f i r s t h a r d l a y e r of snow. A t n i g h t t h e m e l t - w a t e r f r o z e , p r o d u c i n g a n i c e l a y e r which g r a d u a l l y e n l a r g e d a s m e l t i n g c o n t i n u e d . F i g u r e 3, showing r e p r e s e n t a t i v e snow p r o f i l e s of t h e n a t u r a l and d u s t e d s i t e s , i l l u s t r a t e s t h e g r o ~ v t h of t h i s i c e l a y e r a f t e r 2 and 6 days. Although t h e r e was a marked d e c r e a s e i n t h e d e p t h of t h e snow a t t h e d u s t e d
s i t e , t h e r e was n o t a marked d e c r e a s e i n t h e t o t a l w a t e r e q u i v a l e n t of t h e snow c o v e r l ~ h e n compared w i t h t h e undusted a r e a .
On 1 2 March a s n o w f a l l of 1 0 t o 1 2 i n . o c c u r r e d . The a l b e d o o f b o t h t h e d u s t e d and c o n t r o l snow s u r f a c e s i n c r e a s e d t o o v e r 60 p e r c e n t . J i t h t h e w e a t h e r c o n d i t i o n s t h a t p r e v a i l e d ,
it
was 6 t o 7 days a r t e r t h e new s n o w f a l l b e f o r e t h e a l b e d o of t h e d u s t e d s i t e was a c a i n l o w e r t h a n t h e undusted s i t e . F i g u r e 4 ( a ) compares t h e a l b e d o of t h e d u s t e d s u r f a c e ( 4 0 0 gm/metre) w i t h t h a t of t h e c o n t r o l s u r f a c e . F i g u r e 4 ( b ) i s a comparison of t h e t o t a l lwater e q u i v a l e n t of t h e d u s t e d and c o n t r o l snolv c o v e r durin,n t h e r n e l f i n ~ p e r i o d . 3 e c a ~ s e t h e snow c o v e r was l a y e r e d and c o n t a i n e d i c e l e n s e s o f vary in^ t h i c k n e s s , t h e t o t a lw a t e r e q u i v a l e n t c o u l d n o t be measured a c c u r a t e l y .
The snow c o v e r was c o m p l e t e l y melted a t t h e t w o
d u s t e d p l o t s by 22 Xarch, a b o u t 4 days e a r l i e r t h a n t h e
a d j a c e n t u n d i s t u r b e d snow c o v e r . Small a r e a s of t h e a d j o i n - i n g snow c o v e r , however, were c o n t a m i n a t e d b;r c a r b o n
d e p o s i t s f'rom a n e a r b y steam p l a n t and melted c o a p l e t e l : ~ a t a b o u t t h e same t i m e a s t h e d u s t e d snow.
I c e - C o v e r D u s t i n g T e s t s
A l l t h e ic e - t e s t s i t e s were l o c a t e d on t h e i c e c o v e r of a towing t a n k s i t u a t e d a t t h e T a t i o n a l 3 e s e a r c h C o u n c i l grounds i n Ot-tax7!a, with t h e e x c e p t i o n of t h e c a r b o n - b l a c k t e s t s i t e which was l o c a t e d a t a n unused q u a r r y . 7 i g u r e 5 i s a e e n e r a l view of some of t h e t e s t p l o t s s e v e r a l d a y s a f t e r d u s t i n g ( o n 15 ;\:arch).
The - t e s t s i t e s c a n be i d e n t i f i e d by numbers which c o r r e s p o r ? t o t h e numbers s h o m i n Table I. F i g u r e 6 , showing r e p r e s e n t a t i v e i c e p r o f i l e s , i l l u s t r a t e s t h e sequence of i c e m e l t i n g . I n t h e f i r s t s t a g e , a c c e l e r a t e d m e l t i n g was q u i t e e v i d e n t a t a l l t e s t s i t e s , and a f t e r 5 t o 6 d a y s t h e d e p t h of m e l t - w a t e r a t t h e t e s t s i t e s v a r i e d from a maximum of 8 i n . f o r t e s t a r e a
No.
1 t o a minimum of 4 i n . f o r t e s t a r e a Bo. 4( F i g u r e 5 ) . The i c e s u r f a c e u n d e r t h e w a t e r was q u i t e honeycombed, w i t h t h e d u s t p a r t i c l e s embedded i n t h i s
s u r f a c e . T e s t a r e a No. 4 ( w i t h j u s t t h e snow removed) and t e s t a r e a No. 6 ( c a r b o n - b l a c k ) d i d n o t have t h i s hone:~coqbed s u r f a c e . I n t h e s e c a s e s t h e l8!ater-ice i n t e r f a c e was
smooth. On c o l d n i g h t s up t o 1 i n . of i c e ~vould. form on t h e w a t e r s u r f a c e and u s u a l l y would n o t m e l t b e f o r e noon of t h e n e x t day. I n t h e l a t e r s t a g e s , t h e w a t e r d e p t h a t a l l t e s t s i t e s r e a c h e d a b o u t 3 i n . and remained a t a p p r o x i m a t e l y t h a t d e p t h t h r o u g h o u t t h e m e l t i n g p e r i o d ( P i g u r e 5 , f i n a l p r o f i l e ) . The i c e c o m p l e t e l y m e l t e d a t a l l t e s t s i t e s a b o u t 6 A p r i l . Once a l a y e r of w a t e r had d e v e l o p e d on t h e i c e c o v e r t h e m e l t i n g p r o c e s s was t h e same f o r a l l s i t e s . The incoming s h o r t - w a v e r a d i a t i o n was a b s o r b e d k:r t h e ]\.rater s u r f a c e , r a i s i n g t h e t e m p e r a t u r e o f t h e ~ m a t e r and a c c e l e r - a t i n e t h e m e l t i n g of t h e m d e r l y i n g i c e by c o n v e c t i o n . A c e r t a i n p e r c e n t a g e of The s h o r t - w a v e r a d i a t i o n would p e n e t r a t e t h e w a t e r and be a b s o r b e d b y t h e d u s t e d i c e s u r f a c e u n d e r t h e w a t e r . h f t e r t h e w a t e r d e p t h had r e a c h e d C i n . t h e r a t e of m e l t i n g of t h e i c e c o v e r a t t h e d u s t e d s i t e s e q u a l l e d t h a t of t h e n a t u r a l i c e c o v e r . The t e s t s i t e s t h a t had a s l o w e r m e l t i n g r a t e t o b e g i n w i t h ( t e s t s i t e No. 4
w i t h j u s t t h e snow removed) " c a u g h t up" w i t h t h e t e s t s i t e s which a t f i r s t had a f a s t e r r a t e of i c e m e l t i n g . These e x p e r i m e n t s i n d i c a t e t h a t once a l a y e r o f w a t e r i s p r e s e n t
on t h e i c e c o v e r t h e i n i t i a l d e n s i t y of a p p l i c a t i o n of d u s t becomes of s e c o n d a r y importance i n d e t e r m i n i n g t h e m e l t i n g r a t e . Although t h e a c c e l e r a t e d r a t e of m e l t i n , ? was l i m i t e d t o t h e e a r l y s t a g e s o f m e l t , t h e i c e c o v e r a t t h e t e s t p l o t s c o m p l e t e l y melted a b o u t 1 0 d a y s b e f o r e t h e n a t u r a l i c e c o v e r . F i g u r e
7
compares t h e m e l t i n g r a t e of t e s t s i t e No. 1 w i t h t h e m e l t i n g r a t e of t h e n a t u r a l i c e c o v e r on t h e towing t a n k and on a s m a l l l a k e i n t h e a r e a . F i g u r e7
a l s o shows a comparison of t h e a l b e d o of t h e n a t u r a l i c e c o v e r and t h e a l b e d o of t e s t s i t e Eo. 1. I n t h e e a r l y s t a g e s of m e l t i n g t h e a l b e d o of t h e d u s t e d t e s t p l o t was 1 0 t o 20 p e r c e n t compared t o t h e a l b e d o of 50 t o55
p e r c e n t f o r t h e n a t u r a l i c e c o v e r . A s t h e n a t u r a l i c e c o v e r c o n t i n u e d t o q e l t t h e a l b e d o went down t o 20 t o 30 p e r c e n t . B r l y i n A p r i l t h e a l b e d o of b o t h t h e d u s t e d and n a t u r a l s u r f a c e s i n c r e a s e d f o r a b r i e f p e r i o d b e c a u s e of nel.v s n o w f a l l . On7
A p r i l s p r i n g r a i n r e s u l t e d i n a w a t e r - c o v e r e d i c e s u r f a c e w i t h a n e s t i m a t e d a l b e d o of 1 0 t o 1 5 p e r c e n t . I t was e s t i m a t e d t h a t t h e i c e c o v e r remained a t t h i s low a l b e d o f o r t h e r e m a i n d e r of t h e m e l t p e r i o d . The 1362 e x p e r i m e n t s i n d i c a t e d t h a t t h e t y p e of m a t e r i a l , s i z e of p a r t i c l e and r a t e of a p p l i c a t i o n oi" t h e d u s t i n g were n o t t o o c r i t i c a l , and t h a t a l m o s t a n y d a r k m a t e r i a l , u n d e r f a v o u r a b l e w e a t h e r c o n d i t i o n s , c o u l d i n i t i a t e m e l t i n g . I n 1363it
was d e c i d e d t o i n v e s t i g a t e f u r t h e r , b y l a r g e r s c a l e t r i a l s , some a s p e c t s of i c e d u s t i n g . The purpose of t h e s e a d d i t i o n a l e x p e r i m e n t s was t o ( a ) i - n v e s t i - g a t e whether s i m p l y removing t h e snow c o v e r was a s e f f e c t i v e a s d u s t i n g ; ( b ) f i n d o u t if a p p l y i n g t h e dus t on t o g o f t h e snow was a s e f f e c t i v e a s a p p l y i n g t h e d u s t on t h e i c es u r f a c e luith t h e snom removed and ( c ) d e t e r m i n e some of t h e problems a s s o c i a t e d w i t h d u s t i n g a l a r y e r a r e a .
The t r i a l s were conducted d u r i n e t h e s p r i n g of 1963 i n c o - o p e r a t i o n w i t h Marine S e r v i c e s , D ~ p a r t m e n t of T r a n s p o r t , on a s e c t i o n o f t h e g i d e a u Canal a t B u r r i t t l s ~ ' i a p i d s a b o u t 30 a i l e s s o u t h of Ottal-va. Three t e s t s i t e s were e s t a b l i s h e d , e a c h 1 0 0 f t s q u a r e . T e s t s i t e
"A"
rva sd u s t e d a f t e r t h e snow was removed from it. T e s t s i t e "i3"
had t h e snoi;s removed :€ran
it
b u t no d u s t was a p p l i e d . A tof t h e snow. The m a t e r i a l used was a f i n e - g r a i n e d washed sand a v a i l a b l e l o c a l l y and was a p p l i e d by men w i t h s h o v e l s a t a n e s t i m a t e d d e n s i t y o f 400 gm/sq m e t r e . F i g u r e 8 i s a view o f t e s t s i t e A t h e d a y t h e d u s t was a p p l i e d .
'?hen t h e d u s t was f i r s t a p p l i e d on
5
'darch t h e f o l l o w i n g a l b e d o was measured: Cover Albedo N a t u r a l snow c o v e r 71.5 p e r c e n t 4-6 i n . t h i c k Sanded a r e a T e s t s i t eA
Snow removed b y t r a c t o r ( a l i g h t c o v e r i n g ofa
i n . l e f t on) >how c o m p l e t e l y removed ( s c r a p e d t o i c e ) 1 4 . 5 p e r c e n t ( a h a l f h o u r a f t e r d u s t i n g , m e l t l n g v a s o b s e r v e d and t h e d.usted surfac,: n a s c o v e r e d w i t h a l a y e r of w a t e r ) 53.5 p e r c e n t 4s' p e r c e n t F i ~ u r e3
g i v e s d a i l y a i r t e m p e r a t u r e s , p r e c i p i t a t i o n and short-wave r a d i a t i o n v a l u e s f o r ? : a r c h 1963 a t Ottawa. These w e a t h e r r e c o r d s , t a k e n a b o u t39
n i l e s n o r t h of t h e d u s t i n g s i t e , a r e c o n s i d e r e d t o be reasonabl!r r e p r e s e n t a t i v e of w e a t h e r c o n d i t i o n s t h a t ? r e v a i l e d d v r i n c d u s t i n g t r i a l s . Unfavourable w e a t h e r c o n d i t i o n s f o r i c e d u s t i n g p r e v a i l e d t h r o u q h o u t !'larch. On 6 blarch t h e day a f t e r d u s t i n g , t h e t e s t p l o t s were c o v e r e d w i t h 2&i n .
oP heavy, v e t snow. Zxcept f o r t h r e e d a y s , 2 , 1 3 and 2 1 i a r c h , t h e d a i l ? ~ a i r t e r n p e r a t u s e remained w e l l below 30'7 u n t i l 2 4 ;.;arch. Xven on c l e a r da:rs, i t v a s t o o c o l d f o r d u s t i n ? t o ke e f f e c Live.& r i n g t h i s p e r i o d t h e t e s t s i t e s were c o v e r e d by var:,rinr amounts of new snolv. T h e snolv c o v e r 1vas removed
i n g e t t i n g t h e n e c e s s a r y equipment on t h e i c e t h e 2 i n . of snow t h a t f e l l on 20 March was n o t removed. This new snow cover d i d n o t melt from t h e t e s t p l o t s u n t i l 2 1 Pilarch, and even t h e n p o r t i o n s of t h e dusted a r e a s remained
p a r t i a l l y covered. Figure 1 0 shows t h a t t h i s new snow l e f t unmelted "ridges1' a t b o t h t e s t s i t e s A and C .
For a s h o r t period ( 2 4 t o
27
arch) t h e i c e covers a t p l o t s A and C melted a t an a c c e l e r a t e d r a t e , s o t h a t m e l t i n g of t h e i c e cover was e s t i m a t e d t o be a p p r o x i - mately 2 daysi n
advance of t h e m e l t i n g of t h e surrounding i c e cover. P l o t B, where j u s t t h e snow was removed, melted a t a b o u t t h e same r a t e a s t h e n a t u r a l i c e cover. Removing t h e snow cover o n l y was n o t t o o b e n e f i c i a l a t t h i s s i t ebecause t h e underl$ing i c e was q u i t e n h i t e , v i t h a r e l a t i v e l y h i g h a l b e d o (56 F c r c e n t ) .
Rapid m e l t i n g o f a l l p l o t s and t h e n a t u r a l cover occurred f r o m 2 9 klarch t o 2 A p r i l . The i c e cover a t t h e s i t e was flooded by w a t e r d r a i n i n g from m a r b y f i e l d s . By 4 A p r i l
t h e r e was open water a l o n g t h e edge of t h e c a n a l and t h e i c e cover a t a l l s i t e s was e i t h e r water-covered o r i n a n advanced s t a g e of melting.
I)iscussion of 1953 I c e - D u s t i n g T r i a l s
Although 1963 was an example of a 'l-poor" y e a r f o r a c c e l e r a t i n g t h e m e l t i n e of i c e b y d u s t i n c , much u s e f u l i n f o r m a t i o n was o b t a i n e d , p a r t i c u l a r l y from an o p e r a t i o n a l p o i n t of view.
In a n a r e a where t h e r e i s f r e q u e n t snolxf'all
d u r i n g t h e m e l t i n g p e r i o d , it w i l l he d i f f i c u l t
t o
kee? t h e dusted s u r f a c e f r e e o f snow. Even an i n c h o r l e s s of snow can e f f e c t i v e l y cover t h e d u s t e d s u r f a c e and reduce t h eamount of s o l a r r a d i a t i o n absorbed. ( F o r example on
5
illarchremoving
$
i n . of snow f r o m t h e white i c e decreased t h e a l b e d o from 63.5 t o 46 p e r c e n t . ) I t !?#as a l s o noted t h a tsmall amounts of new snow can d r i f t i n t o t h e d u s t e d a r e a and e f f e c t i v e l y c o v e r t h e s u r f a c e .
Another problem i s t o h o w when f i r s t t o a p p l y t h e d u s t . I f t h e o p e r a t i o n i s s t a r t e d t o o e a r l y much n e e d l e s s snow c l e a r i n g o r r e - d u s t i n g w i l l be needed. I f
t h e o p e r a t i o n i s s t a r t e d t o o l a t e , f a v o u r a b l e weather c o n d i t i o n s might be missed.
B e f o r e a d e c i s i o n i s made t o d u s t , r e - d u s t o r remove snow, it would be d e s i r a b l e t o know f u t u r e w e a t h e r c o n d i t i o n s . Tliere would be no p o i n t i n d u s t i n g if a l a r g e s n o w f a l l o r i f s s v e r a l d a y s of u n f a v o u r a b l e c o l d w e a t h e r were e x p e c t e d . The 1963 t r i a l s d e m o n s t r a t e d t h a t t o p l a n
d u s t i n g o p e r a t i o n s e f f e c t i v e l y , r e l i a b l e w e a t h e r f o r e c a s t s a r e needed.
Durine t h e 1962 and 1963 e x p e r i m e n t s , i t !vas observed t h a t d u s t i n g was n o t e f f e c t i v e u n t i l t h e a v e r a g e d a i l y a i r t e m p e r a t u r e was c l o s e t o 30 t o 32OF. If n i g h t - t i m e t e m p e r a t u r e s go much below f r e e z i n g t h e m e l t - w a t e r on t h e d u s t e d s u r f a c e m i l l f r e e z e and on t h e f o l l o w i n g d a y much of t h e a v a i l a b l e s o l a r e n e r g y i s used t o m e l t t h i s new i c e . I n L a r c h 1 9 6 % t h e r e s e v e r a l p e r i o d s when t h e incoming s o l a r r a d i a t i o n vvss w e l l above a v e r a g e . (The Iiarch 1963 t o t a l was 1 0 , 2 0 0 c a l / s q cm, o n l y s l i g h t l y S e l o l s a v e r a g e . ) 'B.ese p e r i o d s o c c u r r e d e i t h e r when t h e a i r
t e m p e r a t u r e was too c o l d f o r i c e d u s t i n p o r between p e r i o d s of l i g h t s n o w f a l l when t h e d u s t e d i c e was e f f e c t i v e l : ?
b l a n k e t e d wi-th sno1.v
ANALYSIS OF 7EATHEH mCOilDS
Using t h e e x p e r i e n c e g a i n e d i n t h e 1952 and 1 ? 5 3 t r i a l s , w e a t h e r r e c o r d s from s e v e r a l l o c a t i o n s a c r o s s ?anada were a n a l y z e d t o d e t e r m i n e how f r e q u e n t l y d u s t i n g y.vould
a p p r e c i a b l y a c c e l e r a t e t h e m e l t i n ? of i c e c o v e r s . 'The s t a t i o n s c?iosen were: Seven I s l a n d s , Ottawa, Kapuskasing, S a s k a t o o n , " r o b i s h e r ;3a:r, Aklavik(Inuvi1c)
,
; ? e s o l u t e .D a i l y v a l u e s f o r a i r temperatv.re, in con in^ zhort-wave r a d i a t i o n and p r e c i p i t a t i o n f o r a b o u t a month % e f o r s n a t u r a l i c e m e l t i n g commenced were o b t a i n e d from
s e v e r a l .rears of r e c o r d s a t e a c n s t a t i o n . These v a l ~ i e s were p l o t t e d + o r e a c h y e a r a t each s t a t i o n i n t h e same -:ay a s Tor t h e Ottalxa r e s u l t s of 1352 and 1753 ( P i f f u r e s 1 and 2).
The p e r i o d s when c o n d i t i o n s rvould have b e e n
f a v o u r a b l e f o r d u s t i n g were o b t a i n e d f o r e a c h y e a r b y a s s u m i n ? t h a t a v e r a c e d a i l y a i r tempera-ture would have t o be above 25OF l o r a t l e a s t two c o n s e c u t i v e da:?s ? o r s o u t l ~ e r n s t a t i o n s , and above 20°? f o r a t l e a s t two c o n s e c u t i v e da:rs f o r A r c t i c
s t a t i o n s . -Past s t u d i e s ( 1 ) i n d i c a t e d t h a t i T t h e d a i l y a i r t e n p e r a t u r e i s l c s s t h a n 25OF i n -the s o u t h , o r 2 0 ° 7 i n t h e
A r c t i c , h e a t l o s s e s f r o m t h e i c e s u r f a c e rlvould o f f s e t an.v e x t r a h c a t r a i n e d a s a r e s u l t of d u s t i n g t h e ic e s l ~ r f a c e . % s t e x p e r i e n c e a l s o i n d i c a t e d t h a t new s n o w f a l l , ~ r e a t e r t h a n 1 . 0 i n . would e f f e c 3 i v e l p c o v e r t h e d u s t e d i c e and a c c e l e r a t e d m e l t would n o t t a k e p l a c e u n t i l t h e snow m e l t e d . I t was t h e r e f o r e assumed t h a t d a y s \ v i t h n e s s n o w f a l l ~ r e a t c r t h a n 1 i n . would n o t be s u i t a b l e f o r d u s t i n g .
Some a d d i t i o n a l a s s u m p t i o n s were a l s o made.
F i r s t , it !vas assumed f o r t h e c a l c u l a t i o n s t h a t i f c o n d i t i o n s were f a v o u r a b l e , t h e a l b e d o ( p e r c e n t a g e of s o l a r r a d i a t i o n r e f l e c t e d ) of i c e would be r e d u c e d f r o m 50 t o 2 0 p e r c e n t 5:r
d u s t i n q . l%us, t h e a d d i t i o n a l s o l a r e n e r p v ?lade a v a i l a b l e b.7 d u s t i n a was ass~zmed t o e q u a l 30 p e r c e n t of t h e in corn in^
s o l a r r a d i a t i o n . Second, it was assumed t h a t t h e s u r r a s e 7 n r o ~ ~ l d allnrays he d u s t e d on t h e f i r s t d a y of a f a v o u r a b l e ~ e r i o d . This a s s u m p t i o n i m o l i e s t h a t r e l i a b l e w e a t h e r
forecast in^ would be a v a i l a b l e , and t h a t i f n e c e s s a r v , t h e i c s s u r f a c e 7vo11ld be d u s t e d s e v q r a l t i m e s . F i n a l l y , it IFras a s s u q e d t h a t i f t h e d a i l y a v e r a p e a i r t e m ~ e r a t u r e lvas a b o v e
35'1'
f o r f i v e c o n s e c u t i v e d a ~ r s , n a t u r a l i c e m e l t i n p lvould s t a r t and i c e d u s t i n g vvould n o l o n p e r a c c e l e r a t e m e l t i n - . T n i s a s s u m ~ t i o n i m p l i e s t h a t once n a t u r a l m e l t i n q b e r i n s , +;he a l b e d o o f t h e s ~ ~ r f a c e i s lowered t o t h a t of a d u s t e d s u r f a c ~ ( a b o u t 20 7 e r c e n t ) .The t o t a l incoming s o l a r r a d i a t i o n d u r i n g the
p e r i o d s when i c e d u s t i n g lvould have b e e n lfi~o.rthlvhile was
t a b u l a t e d f o r e a c h ;rear f o r e a c h s t a t i o n . Tor two s t a t i o n s , i t was n e c e s s a r y t o e s t i m a t e a v e r a c e s o l a r r a d i a t i o n f r o q
t h e l a t i t u d e and t i ~ e of y e a r . T a b l e I1 l i s t s t h e s t a t i o n s and t h e number o f y e a r s a n a l y z e d , and g i v e s t h e t o t a l
i n c o m i n g s o l a r r a d i a t i o n of t h e v o r s t , a v e r a g e and b ~ s t y e a r s . A t s e v e r a l s t a t i o n s , t h e v o r s t y e a r had n o f ' a v o u r a t . 1 ~ i c e - d u s t i n g p e r i o d s , a n d , t h e r e f o r e , t h e v a l u e f o r inn,o:nin.? s o l a r r a d i a t i o n was z e r o . The e s t i n a t e d s o l a r r a d i a t i o n d i n i n g t h e i c e - d u s t i n p p e r i o d s f o r e a c h y e a r and e a c h s t a t i o n ;vas c o n v e r t e d t o i n c h e s of i c e m e l t by m u l t i p l y i n g b y 30 p e r c e n t , and a s s u m i n ~ r th e h e a t of f u s i o n of i c e e q u a l t o C O c a l . / - a . I n F i z u r e 11, t h e s e v a l u e s a r e p l o t t e d on f r e q u e n c y dia,yrems f o r e a c h s t a t i o n t o show t h e v a r i a t i o n i n estirnatec! a d d i t i o n a l . q e l t . From t h i s d i a c r a m , t h e number of t i m e s a d d i t i o n a l q z l t 7.vould exceed a c e r t a i n v a l u e c a n b e e s t i m a t e d . F o r e x a m p l e , a t O t t a v a , o n l y i n two y e a r s o u t of e l e v e n would t h e a d d i t i o n a l rnelt due t o i c e d u s t i n q e x c e e d 6 i n . A t ? ? e s o l u t e , t h e e s t i m a t e d a d . d i t i o n a 1 m e l t exceeded 6 i n . e v e r y ?rear d u r i n c : t h e t z n y e a r s examined.
I n making c o m p a r i s o n s b e t w e e n t h e n o r t h e r n and s o u t h e r n s t a t i o n s , it s h o u l d be remembered t h a t 6 i n . of a d d i t i o n a l m e l t r e p r e s e n t s a b o u t 25 p e r c e n t of t h e t o t a l i c e ( 2 f t ) t o be m e l t e d i n t h e s o u t h , b u t l e s s t h a n 1 0 p e r c e n t of t h e t o t a l i c e ( 5 f t p l u s ) t o be m e l t e d i n t h e A r c t i c . m e maximum e s t i m a t e d n e l t i n t h e s o u t h i s a b o u t 1 2 i n . o r 50 3 e r c e n t of t h e t o t a l i c e , comnared t o a maximum of 2 1 i n . o r a b o u t 30 p e r c e n t of t h e t o t a l i c e t h i c k n e s s i n t h e A r c t i c . 'LPhis a n a l T r s i s d o e s n o t a t t e m p t t o d e f i n e how much a d d i t i o n a l i c e need b e m e l t e d t o j u s t i f y a d u s t i n e o p e r a t i o n . 2This w i l l d e ~ e n d on t h e t h i c k n e s s a n d t y p e oC i c e , d u r a t i o n of b r e a k - u p , weakening e f f e c t of d u s t e d i c e c o v e r , and t h e economic b e n e f i t s t o be d e r i v e d from a c c e l ~ r -
at in^
t h e n a t u r a l m e l t i n g p r o c e s s . It a l s o s h o u l d Seemphasized t h a t some of t h e a s s u m p t i o n s made f o r t h e a n a l v s i s a r e q u i t e a r b i t r a r y and i n n r a c t i c e , t h e a c t u a l b e n e f i t d u e t o i c e d u s t i n g q i y h t d i f f e r from t h e c a l c u l a t e d b e n e f i t . l'rov t h e p r e s e n t a n a l ; ~ s i s , it c a n be c o n c l u d e d , however, t h a t a t a l l s t a t i o n s t h e r e w i l l Pe y e a r s when i c e dust in^ would b e of l i m i t e d t o no v a l u e . I n t h e s o u t h e r n s t a t i o n s , i c e - d u s t i n g y e a r s o c c u r q u i t e f r e q u e n t l - y . The e s t i m a t e d a d d i t i o n a l n e l t was u n d e r 3 i n . s i x t i m e s o u t of e l e v e n a t O t t a w a , f o u r t i m e s o u t of t e n a t ;even I s l a n d s . I n n a k i n g s u c h a n a n a l y s i s , i t m s t b e a p p r e c i a t e d t h a t t h e time of b r e a k - u p , e x p e c t e d a i r t e l n p e r a t u r e , sno!rifall and r a d i a t i o n w i l l n o t b e known a t t h e tirlle d u s t i n a i s
c o n t e m p l a t e d . ' f i e o n l y p r o c e d u r e t h a t c a n kc! f o l l o w e d -l-s t o d u s t ~'vhenever r e q u i r e d i f t h e s h o r t - t e r n eather her f o r e c a s t i s f s v o u r a b l e . A r i n ? "poor" d u : j t i n ~ :r e a r s , s:lch a p r o c e d u r e
i s boimd .to r e s u l t i n much masted d u s t i n g .
I n a s s e s s i n ? t h e p o s s i b l e v a l u e of d u s t i n v t h e t h r e e n n i n f a s t o r s t l ~ a * must be consj.dered q r e :
(1) 7:vea t h e r c o n d i t i o n s
( 2 ) i c e o r snoi7l c o n d i t i o n s ( i n c l u d i n ? s i t e c o n d i t - i o n s ) and
( j) ,-lu:; bin,? ~ n a t e r i a l ( i n c l l l d i n y t:rne, r a $ e nP
a p p l i c a i i o n and a v a i l a b i 1 i t : r of a s ~ ~ i t a b l e econoinical d u s t )
.
Prom t h e a n a l y s i s o f p a s t w e a t h e r r e c o r d s a t s e v e r a l s t a t i o n s i t i s concluded t h a t
at
most p l a c e s i n Canada t h e amount of i c e t h a t can be melted by i c edust in^
v a r i e s c o n s i d e r a b l : ~ f r o m y e a r t o g e a r - t h e amount of i c e t h a t c a n be m e l t e d d u r i n c a f a v o u r a b l e y e a r b e i n g sevevral t i q e s g r e a t e r t h a n t h e amount t h a t can be q e l t e d durincr a n u n f a v o u r a b l e :rear. T3ecause of t h i s v a r i a t i o n , a v a i l a b l e w e a t h e r r e c o r d s s h o u l d be examined a t a s i t e kef'ore i c e - d u s t i n s o p e r a t i o n s a r e coqmenced. snolJJ o r i c e c o v e r c o n d i t i o n s t h a t e x i s t a t 8 s i t e a r e i m p o r t a n t i n a s s e s s i n s t h e f e a s i b i l i t y of d u s t i n ; I c e . If t h e a l b e d o of t h e n a t u r a l s u r f a c e t e n d s t o r e n a i n h i g h b e f o r e and d u r i n g t h e a c t i v e m e l t p e r i o d , t h e opncr*unit~ f o r a c c e l e r a - t i n s t h e n a t u r a l x e l t ra-te i n c r e a s e s . J ~ ; r d , c i n ~ f r o m t h e r e s u l t s of t h e 1962 and 1363 e x p e r i 9 e n t s on i c e c o v e r s , i t i s onl;r i n t h e e a r l y s t a g e s of m e l t nhen t h e i c e c o v e r i s snov covered t h a t t h e a l b e d o of f r e s h w a t e r i c e i s h i g h . I n t h e l a t e s t a g e s of m e l t i n g when t h e i c e o r snonr c o v e r becomes lvet, t h e a l b e d o d . e c r e a s e s t o a low v a l u e . The s u r f a c e c o n d i t i o n s and hence t h e a l b e d o p r o b a b l y d o e s var;! f r o n y e a r t o y e a r a t t h e same s i t e . B r i a z g i n ( 3 ) i n d i c a t e s t h a t t h e a l b e d o of i c e observedat
d r i f t i n g i c e s t a t i o n s can v a r y from a naximum of o v e r 90 p e r c e n t , w i t h f r e s h l y f a l l e n snow, t o a minimum of 1 0 t o 20 p e r c e n t with m e l t puddles on t h e i c e . F a c t o r s such a s f l o o d i n g of t h e s u r f a c e by n ~ n - o f fo r r a i n , d r a i n a g e of e x c e s s w a t e r from t h e i c e s u r f a c e ,
surTace r o u g h n e s s , d r i f t e d snow, c r a c k p a t t e r n s i n i c e - 21-1 can a f f e c t t h e a l b e d o .
'The e a s e ivitln which t h e e x c e s s m e l t - w a t e r proc7,uced by d u s t i n p can 'ce d r a i n e d from a s i t e i s o r importance i n
a s s e s s i n p t h e p o t e n t i a l v a l u e of d u s t i n g . I n lr?52 t h e e x c e s s m e l t - w a t e r a t t h e snow c o v e r t e s t s i t e accumulated a t t h e
s i t e . If it h a d been p o s s i b l e t o d r a i n o f f t h i s m e l t - w a t e r ( f o r example i f t h e snow c o v e r was on s l o p i n ? pavement) t h e snow c o v e r would have melted s o o n e r . I n t h e c a s e of t h e 1'?52 i c e t e s t s i t e s , i f it had been p o s s i b l e t o d r a i n t h e m e l t
';ales s o t h a t t h e d u s t e d s u r f a c e was c o n t i n u a l l y exposed t o
incoming s o l a r r a d i a t i o n , v e r y r a n i d a c c e l e r a t e d a e l t i ~ y c o u l d have been a c h i e v e d . If t h e n e l t r a t e d e c r e a s e s a f t e r t h e m e l t h o l e s have r e a c h e d a d e p t h of 8 i n . k e c a u s e t h e w a t e r c a n n o t be d r a i n e d from t h e s e h o l e s , t h i s coul(1 be a s e r i o u s l i q i t a t i o n t o t h e i c e - d u s t i n g t e c h n i q u e , even u n d e r o t h e r w i s e f a v o u r a b l e c o n d i t i o n s . I n t h e A r c t i c , w i t h s e v e r a l f e e t of i c e t o 'ce m e l t e d , a n i n c r e a s e i n m e l t i n g onl7r durin; t h e t i n e i t t a k e s a h o l e 8 i n . deep t o d e v e l o p would p r n t a b l y n o t a p n r e c i a b l y a c c e l e r a t e t h e n a t u r a l m e l t i n ? r a t e .
T h e s e e x p e r i m e n t s h a v e i n d i c a t e d t h a t t h e w e a t h e r a n d snow o r i c e c o n d i t i o n s t h a t p r e v a i l d u r i n g i c e - d u s t i n g t r i a l s a r e o f f i r s t i m p o r t a n c e i n d e t e r m i n i n y w h e t h e r o r n o t i c e - d u s t i n g o p e r a t i o n s w i l l be s u c c e s s f u l . If t h e s e c o n d i t i o n s a r e f a v o u r a b l e i t s h o u l d n o t b e d i f f i c u l t t o d e v e l o p t e c h n i q u e s f o r a p p l y i n g s u i t a b l e d u s t s . O t h e r t e c h n i q u e s s u c h a s s p r a y i n g d:res on i c e o r pumping s e a w a t e r on i c e , c o u l d a l s o b e c o n s i d e r e d a n d d e v e l o p e d . Anv f u t u r e program t o a s s e s s t h e v a l u e of i c e d u s t i n p s h o u l d b e u n d e r t a k e n o n l y where w e a t h e r a n d i c e c o n d i t i o n s a p p e a r t o b e f a v o u r a b l e f o r s u c h t r i a l s a n d where t h e p o t e n t i z l b e n e f i t s w a r r a n t l a r g e - s c a l e t r i a l s . The a u t h o r w i s h e s t o a c k n o v l e d g e t h e h e l p of
P. hlontf o r d i n making many of t h e o b s e r v a t i o n s a n d t h e
a d v i c e of L . 7 . Gold i n t h e p r e p a r a t i o n of t h e r e p o r t . The c o - o p e r a t i o n o f p e r s o n n e l of t h e l I a r i n e S e r v i c e s , D e p a r t q e n t of T r a n s u o r t
,
p a r t i c u l a r l ; ~ U. J . L o r t i e , d i d e a u C a n a l ?n:yineer, i s ~ r a t e f u l l y a c k n o w l e d ~ e d .1. ',Villiams, G.P. and L.Y. Gold. The u s e of d u s t t o advance t h e b r e a k - u p of i c e on l a k e s and r i v e r s . ,Proceedings of t h e E a s t e r n Snow C o n f e r e n c e , F e b r u a r y 1 9 6 5 , p. 31-56. 2 . A r n o l d , K.C. An i n v e s t i g a t i o n i n t o methods of a c c e l e r a t i n g t h e , m e l t i n g of i c e and snow by a r t i f i c i a l d u s t i n g . Geology of t h e A r c t i c
-
Vol. 11, U n i v e r s i t y of Toronto ?ress 1961, p. 989-1013.3.
B r i a z g i n , N.N.K
voprosu ob a l l b e d o p o v e r k h n o s t i d r e i f u i ~ ~ s h c h i k h l ' d o v . (The problem of t h e a l b e d o on t h e s u r f a c e of d r i f t i n g i c e . ) ? r o b l e n v Ar?rt,iki i h n t a r k t i k i , KO. 1, 33-33, 1959. T r a n s l a t e d byR i c h a r d Ifi. Holden f o r Geophysics Research D i r e c t o r a t e , A i r Force Research D i v i s i o n ,
I,.
G. Hanscom F i e l d ,TABLE
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5450 0710 B e s t y e a r 1 1 , 7 0 0 e l 0 0 5130 'q15 , 1 0 , GOO 1 1 , 0 0 0 1 3 ,'700 -Active N a t u r a l Melt Begins P R E C l P I T A T I O N 2 4 6 8 10 12 14 16 1 8
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22 24 26 28 30 1 3 M A R C H 1962 A P F I L A I R T E M P E R P . T ( J R E , P R E C I P I T A T I O N , S H O R T - W A V E R A D I A T I O N a T T A W A , M A R C H 1 9 6 2PIGURI;: 2a Kipp R a d i o m e t e r
-
March 1362-
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7 4, 11 13 15 17 19 21 23 25 M A R C H , 1 9 6 2 F I G U R E 4 C O M P A R I S O N O F A L B E D O A N D W A T E R E Q U I V A L E N T , N A T U R A L A N D D U S T E D S N O B , O T T A W AFIGURE
5
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FIGURE
8 View of ice-dusting site " A f 1 RurrittlsM A R C H 1963 A P R I L
k l R T E M P E R A T U R E , P R E C I P I T A T I O N , S H O R T - M ; P . V E R A D I A T I O N O T T A W A , M A R C H 1 9 6 3
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