FZAK30 PAFC 232224
ICOAFC

Sea Ice Outlook for Western and Arctic Alaskan Coastal Waters 
National Weather Service Anchorage Alaska 
224 PM AKDT Thursday 23 September 2021

...SEPTEMBER 2021 MONTHLY SEA ICE OUTLOOK...

Looking at the big picture, while sea ice in the Chukchi and 
Beaufort Seas has certainly continued to thin and the ice edge 
retreat back to the north in the past month, the overall sea ice 
extent in Alaska waters is farther south than most of the past 10 
years at this point in the season.   

As we look forward into the start of freeze-up season, the sea 
surface temperatures are cooler than recent years especially across 
the southern Chukchi Sea and northern Bering Sea. So freeze-up in 
these areas may not be quite as delayed as in recent years. Beyond 
October, La Nina conditions are expected to develop again which 
could keep the general storm track across the southern Bering Sea or 
just south of the Aleutian Islands. The area of greatest uncertainty 
through December is south of Nunivak Island in the Bering Sea.

Detailed information can be found in each pertinent section below.

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

Sea ice is expected to begin forming near freshwater river deltas 
and behind barrier islands of the north slope coast of Alaska during 
the last week of September or first week of October. The first new 
ice beyond barrier islands out to 20nm offshore generally begins to 
form about two weeks afterward. Sea ice concentration may reach 7 
tenths out to 20nm offshore during the 3rd week of October. 

From Demarcation Point to Pt. Barrow offshore to 75N, sea ice growth 
is expected to expand south of the ice pack by the end of September. 

Sea ice offshore within the Beaufort Sea is expected to merge with 
the new coastal sea ice during the fourth week of October. 

...FREEZE-UP OUTLOOK FOR THE CHUKCHI SEA...

From Icy Cape to Utqiagvik, the first new sea ice formation is 
expected during the first week of October. This area is expected to 
reach 7 tenths concentration by the end of October. 

Navigational waters around Point Barrow are expected to reach 7 
tenths concentration during the 2nd or third week of October.

For the area from Icy Cape to Utqiagvik offshore west to 170W, the 
first new sea ice is expected by the first week of October. Sea ice 
concentration is expected to reach 7 tenths during the first or 
second week of November and sea ice covered around the middle of 
November. 

For Point Hope to Icy Cape to 20nm offshore, the first new sea ice 
is expected during the second week of October. Sea ice is expected 
to reach 3 tenths concentration by the end of October and reach 7 
tenths concentration during the first or second week of November. 

For the Chukchi Sea from Pt. Barrow north to 75N and west to 170W, 
sea ice concentrations are expected to reach 7 tenths by the first 
week of November. 

For Kotzebue Sound, the first new sea ice is expected during the 
second week of October. Three tenths concentration is expected 
during the first week of November, and 7 tenths concentration is 
expected by the middle of November. 

For Cape Krusenstern to Point Hope to 20nm offshore, the first sea 
ice is expected to form by the end of October. Seven tenths 
concentration is expected around the middle of November.

For Wales to Espenberg to 20nm offshore, the first new sea ice 
behind barrier islands is expected by the fourth week of October. 
Three tenths concentration within navigational waters beyond barrier 
islands is expected around the middle of November, and 7 tenths 
concentration during the 3rd week of November. 

For Wales to Point Hope to 170W, outside of Kotzebue Sound, sea ice 
concentration is expected to reach 3 tenths during the second half 
of November and may reach 7 tenths by the end of November. 

The Bering Strait is expected to reach 7 tenths ice concentration 
within 20 nm of the center line by the end of November.

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

The first sea ice in the Bering Sea will most likely be in Norton 
Bay within Norton Sound. The first sea ice in this area is expected 
to form around the middle of October. Three tenths sea ice 
concentration within Norton Sound is expected around the middle of 
November and 7 tenths concentration is expected by the end of 
November. 

The first sea ice along the Yukon Delta is expected by the end of 
October. Three tenths concentration is expected during the first 
half of November and 7 tenths concentration is expected during the 
second half of November. 

The first sea ice along the Kuskokwim Delta is expected during the 
first week of November. Three tenths concentration is expected 
around the middle of November and 7 tenths concentrations by the end 
of November. 

Sea ice formation within Bristol Bay varies significantly from year 
to year. At this time, we expect the first sea ice formation within 
Bristol Bay during the last week of October or first week of 
November depending when a cold snap occurs around that time. Sea ice 
concentrations are expected to reach 3 tenths by the end of 
November. If cold air remains over the Bristol Bay region, sea ice 
concentrations could reach 7 tenths sometime during December, 
however this is extremely variable from year to year. 

The ice edge is expected to reach Saint Lawrence Island around the 
middle of December. 

The ice edge may reach Saint Matthew Island by the end of December, 
however it is more likely it will reach this point in January.

The coastal sea ice is expected to extend west of Nunivak Island 
around the middle of December. 

...FREEZE-UP OUTLOOK FOR COOK INLET...

Freeze-up can vary widely from year to year within Cook Inlet, as it 
is largely tied to atmospheric temperatures throughout the Cook 
Inlet region during the autumn and early winter. At this point, our 
best idea of when sea ice would begin to form in the most protected 
areas such as Knik Arm, Turnagain Arm, and the Susitna River Delta 
is during the first half of November. 

The first sea ice south of a line from the Susitna River Delta to 
Point Possession to the Forelands may form by the end of November.

Sea ice concentrations north of the Forelands will likely reach 3 
tenths by the middle of December and may reach 7 tenths by the end 
of December.

The first sea ice south of the Forelands is expected to form during 
the second half of December.

$$ 
Schreck