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DRAFT!!      DRAFT!!      DRAFT!!

Posted September 10, 2014

By Elizabeth Dobbins, Research Scientist, UAF

 

Big Blow

Data from Burger and Klondike MetBuoys

Wind speed, direction, and water temperature measured by the industry metbuoy in the Burger (green) and Klondike (red) study areas, Chukchi Sea, Sept. 2014

 

At the beginning of September, a vigorous low in the Beaufort Sea brought significant snowfall to Barrow, AK. Winds there were strong and from the north, and waves caused a lot of erosion along the shoreline. In the Chukchi, winds were consistently 20 knots (see figure). It didn't decrease water temperatures much in Burger, but the more southerly Klondike area experienced a decrease of several degress in water temperature.

By the way, notice how the winds have been edging back up again recently.

Surface Currents from HFR

Surface currents as measured by HFR, Sept. 4, 2014

 

It is not immediately clear from the surface HFR maps how the currents were affected by this weather system. Perhaps, the Alaskan Coastal Current is pushed closer to shore and weakened. However, the drifters were obviously affected, as decribed below.

Drifters

When we last checked in with the drifters, it looked as though the ones in the western Chukchi were moving northward over Herald Valley and the Central Channel. However, then the winds strengthed and shifted, and things changed.

Pt Lay drifters, Sept. 4, 2014

Pt Lay drifters (blue pushpins) on Sept. 4, 2014, with surface currents from HFR.

 

Instead of heading north through the Central Channel, the drifters that had been deployed off Pt. Lay were swept toward the coastline. Their velocity increased quite a bit - they moved farther in a couple days than they had in the previous weeks. As they entered the ACC, what had been a tight pack of drifters sheared along the coast, until they were dispersed almost to Barrow.

Pt Lay drifters, Sept. 10, 2014

Pt Lay drifters (blue pushpins) on Sept. 10, 2014, with shaded bathymetry.

 

Then the wind shifted again, and the drifters sort of stopped. The drifters that had reached the southern rim of Barrow Canyon continued to move toward the Beaufort Sea. Those that had trailed behind went southwest, confirming the divergent flow pattern off Wainwright that was seen during that time in the HFR current maps (not shown).

The drifters that had been released off Point Hope were previously moving northward into Herald Valley. By Sept. 4, these had broken into groups. Of the original 27 drifters, ~4 went up the valley, ~5 moved onto Herald Shoal and remain there, while the rest hover sourtheast of Wrangel Island.

Point Hope drifters, Sept. 4, 2014

Pt Hope drifters (blue pushpins) on Sept. 4, 2014, with shaded bathymetry.

Point Hope drifters, Sept. 10, 2014

Pt Hope drifters (blue pushpins) on Sept. 10, 2014, with shaded bathymetry.

Some Wainwright drifters, Sept. 10, 2014

Selected Wainwright drifters (blue pushpins) on Sept. 10, 2014.

 

Meanwhile, the drifters released at Wainwright had been amongst the sea ice along the shelf-break. They are slowly dispersing as the ice breaks up. Some have moved into the basin, but there haven't been any large shelf-basin exchange events like we have seen in other years (for example in late August, 2012).

With the scattering of all these drifters, we are putting together a nice picture of Sea Surface Temperature (SST) along the edges of the Chukchi Sea:

SST from drifters, Chukchi Sea, Sept. 8, 2014

 

Field Ops

 

News

 


Last modified: September 11 2014 14:12:17.