FZAK30 PAFC 221739
ICOAFC

Sea Ice Outlook for Western and Arctic Alaskan Coastal Waters 
National Weather Service Anchorage Alaska 
938 AM AKDT Thursday 22 April 2021

...APRIL 2021 MONTHLY SEA ICE OUTLOOK...

Looking at the big picture, sea ice within the Bering Sea has been 
fairly stable through April, although its movement has fluctuated 
between north and south as storms moved through the area during the 
month. Sea ice within the Bering Sea has been most steadfast from 
about St. Matthew Island westward. Sea ice within Cook Inlet has 
decreased substantially during April, although it was slow to melt 
in the first half of the month due to below normal air temperatures 
in the region. 

As we look forward in break-up season through July, La Nina 
conditions will continue to weaken in May, giving way to a more 
neutral ENSO state for the summer months. The eastern Bering Sea may 
break up quicker than previous years as winds have repeatedly moved 
sea ice off to the west and the resultant sea ice is now thinner 
than usual. The thicker ice that has come south through the Bering 
Strait this winter is mainly in the central and northern Bering Sea. 
For the remainder of the Bering Sea and southern Chukchi Sea, expect 
a more “normal” breakup, possibly even a little delayed from the 
quicker breakups of the past few years. Farther north across the 
northern Chukchi Sea and Beaufort Sea, multi-year ice will slow 
break-up, perhaps considerably in some areas. 

Detailed information can be found in each pertinent section below.


...BREAK-UP OUTLOOK FOR COOK INLET...

The Forelands to Fire Island is expected to reach 3 tenths 
concentration by the fourth week of April and sea ice free for the 
season during the last week of April. 

Turnagain Arm is expected to be sea ice free during the fourth week 
of April. 

Knik Arm is expected to reach 3 tenths concentration by the third 
week of April and be sea ice free during the last week of April. 

Cook Inlet is expected to be sea ice free outside of Knik and 
Turnagain Arms during the last week of April. 

Cook Inlet is expected to be sea ice free during the last week of 
April. 

...BREAK-UP OUTLOOK FOR THE BERING SEA...

Bristol Bay is expected to reach 3 tenths coverage during the last 
week of April and be sea ice free for the season during the first 
week of May.

For Kuskokwim Bay, shorefast ice will likely no longer be shorefast 
during the first week of May.  Sea ice is expected to reach 3 tenths 
concentration by the second week of May and be sea ice free for the 
season by the third week of May.

Etolin Strait is expected to reach 3 tenths concentration during the 
second week of May then sea ice free for the season during the third 
week of May.

For Etolin Strait to Cape Romanzof to 20 nm offshore, sea ice is 
expected to no longer be shorefast during the second week of May and 
decrease to 3 tenths concentration during the last week of May. This 
area is expected to be sea ice free for the season during the last 
week of May. 

For Cape Romanzof to Kwikpak to 20 nm offshore, sea ice is expected 
to no longer be shorefast during the last week of May and decrease 
to 3 tenths concentration during the first week of June. This area 
is expected to be sea ice free for the season by the second week of 
June.

For Kwikpak to Unalakleet to 20nm offshore, sea ice is expected to 
no longer be shorefast during the last week of May. Sea ice is 
expected to reach 3 tenths concentration by the second week of June 
and become ice free by the third week of June. 

Sea ice near Shaktoolik is expected to reach 3 tenths concentration 
during the third week of May and become sea ice free for the season 
by the end of May.

For Norton Bay, sea ice is expected to no longer be shorefast during 
the last week of May. Sea ice is expected to reach 3 tenths 
concentration by the first week of June and be sea ice free for the 
season by the second week of June. 

For Golovin Bay, sea ice is expected to no longer be shorefast by 
the end of May. 3 tenths coverage then sea ice free conditions are 
expected during the first week of June.

Sea ice along the Nome Coast is expected to no longer be shorefast 
during the last week of May. Sea ice in this area should reach 3 
tenths concentration by the first week of June. Ice free conditions 
are expected during the second week of June.

Norton Sound sea ice less than 3 tenths coverage is expected around 
the middle of June and is expected to become sea ice free during the 
third week of June.

For Port Clarence, ice is no longer expected to be shorefast by the 
first week of June. 3 tenths coverage is expected during  the second 
week of June and sea ice free conditions are expected during the 3rd 
week of June. 

The Bering Sea south of 60N is expected to be sea ice free for the 
season during the last week of May. 

South of Saint Lawrence Island is expected to be sea ice free by the 
end of June.

For Saint Lawrence Island to the Bering Strait, less than 3 tenths 
coverage is expected by the end of June.

The Bering Strait is expected to be ice free to 20nm N/S of a center 
line by the end of June.

The Bering Sea is expected to be ice free by the end of June. 
 
...BREAK-UP OUTLOOK FOR THE CHUKCHI SEA...

For Wales to Espenberg to 20 nm offshore, sea ice is expected to no 
longer be shorefast during the first week of June. Less than 3 
tenths coverage and open water is expected during the 3rd to 4th 
week of June.

Sea ice within Kotzebue Sound may no longer be shorefast by the 
middle of June. Less than 3 tenths coverage is expected during the 
4th week of June. Ice free conditions are likely in the first week 
of July. 

For Cape Krusenstern to Point Hope to 20nm offshore, ice is no 
longer expected to be shorefast by the middle of June. 3 tenths 
coverage is expected during the third week of June and sea ice free 
by the end of June. 

For Point Hope to Wainwright to 20nm offshore, sea ice is expected 
to no longer be shorefast during the 3rd week of June. Sea ice 
concentration is expected to reach 3 tenths by the first week of 
July, and sea ice free for the season during the second half of 
July. 

For Wainwright to Utqiagvik to 20nm offshore, sea ice is expected to 
no longer be shorefast around the end of June or beginning of July. 
Sea ice concentration less than 3 tenths and possibly sea ice free 
conditions for the season can be expected in the second half of 
July. 

From Point Hope to Icy Cape, to 170W, sea ice concentrations less 
than 3 tenths can be expected around the end of June or beginning of 
July. This area will likely be sea ice free for the season by the 
end of July.

From Icy Cape to Utqiagvik to 170W, the timing that sea ice 
concentrations reach less than 3 tenths for the season varies widely 
from early July to late September, even within the last 10 years. 
This year the multi-year ice in the area will likely mean a break-up 
on the later end in this area, likely in August.

...BREAK-UP OUTLOOK FOR THE BEAUFORT SEA...

In general, a large amount of multi-year sea ice in the Alaska 
waters of the Beaufort Sea will mean a later break-up than last 
year. Sea ice will begin to melt out from the Alaska coastline in 
July, then a relatively slow break-up is expected for the remainder 
of the Alaska waters of the Beaufort Sea.

For Point Barrow to Flaxman Island, sea ice is expected to no longer 
be shorefast during the first half of July. 

For Flaxman Island to Demarcation Point, sea ice is expected to no 
longer be shorefast around the end of June or beginning of July. 

$$ 
Schreck