Posted October 27, 2014
By Elizabeth Dobbins, Research Scientist, UAF
The Ice is Coming
Chukchi coast with ice prediction from NOAA's NWS. |
Chukchi coast with HFR vectors showing the effect of the ice. |
Ice has begun moving into our study area along the Chukchi and Beaufort shelves. The areas where the HFR installations provide measurements of surface currents has been steadily decreasing. MODIS real-color imagery is disappearing from the region due to the lack of daylight, but it shows ice hovering offshore, perhaps being pushed along by persistently easterly winds.
Drifters and ice prediction, Oct. 6, 2014
Many of our drifters have gone very far north - much farther than in other years - so they have been persistently along the ice edge. On Oct. 6, 2014, after several days of northerly winds, the drifters looked like they were trying to escape the oncoming ice.
Drifters and ice prediction, Oct. 27, 2014
But resistance was futile. At least a dozen of our drifters are now within areas of >80% ice coverage. The temperatures measured by these drifters are well below freezing, and often go bad, presumably from the sensors being frozen. In 2012, we had several drifters last though the winter, frozen in the sea ice. Odds are that this year's drifters will die soon, but we can hope for such longevity.
Alaska Coastal Current Reversal
Drifters north of Barrow, Oct. 6, 2014
Back in early October, we had many drifters that were headed into the Beaufort Sea after having traveled to the east along Barrow Canyon in the Alaskan Coastal Current (ACC). As in other years, when they reached the shelf break, some went north and some went south. Some did little loops, revealing the eddies we've seen there in other years. But then something different happened.
Some of those Barrow drifters, Oct. 28, 2014
Today, all those drifters have been pushed back onto the Chukchi Shelf and are heading to Wrangel Island. There was a one and a half week period of 20-30 knot winds from the east, and both the north and south drifters turned around and went back past Point Barrow.
During this time, the ACC completely reversed. Winds have relaxed since then, but the ACC has not recovered yet.
Daily averaged surface currents measured by the HFR, Oct. 21, 2014
Field Ops
- 57 drifters remain active of the original 149 drifters deployments sponsored by the North Slope Borough-Shell Baseline Studies program and the ARCTREX program. Only 14 have beached this year.
- The ice is closing in on all 4 HFR sites.
News
- U.S. initiates prototype system to gauge national marine biodiversity: The Chukchi Sea will be the location of a new biodiversity initiative.
- Drifting NTCL barge will likely spend winter in Beaufort Sea ice: Looks like the Beaufort Sea has acquired a new drifter!