The long-term trend for Arctic sea ice is inexorably down. Year-after-year, decade-after-decade, the human-driven accumulation of heat in the Arctic has taken a terrible toll. Recently, mid March through mid April showed record low sea ice extents for any period since record keeping began in 1979.
Over the past two weeks, extent levels bounced back to around 4th to 6th lowest on record as winds shifted to north-to-south through the broad region between Greenland and the Kara Sea. For this region, melt pressure had been quite strong throughout Winter as a powerful warm flow of air flooded up from the North Atlantic.
(Ice in the Bering and the Sea of Okhotsk is rapidly melting. Warming and sea ice melt ramp-up may also be on tap for both the Hudson Bay and the Beaufort as south-to-north air flows associated with the Ridiculously Resilient Ridge intensify. Image source: NSIDC.)
The shift, which has occurred coincident with upper-level winds running up from the Ridiculously Resilient Ridge in the Eastern Pacific, over Alaska and the Northwest Territories of Canada, into the Beaufort and on past the pole, has been pushing sea ice southward toward the Barents and into the Fram Strait. The result has been minor sea ice expansion in the near Greenland region at the cost of much more rapid melt in the Bering Sea, the Sea of Okhotsk and a very earl season break up of ice in the Beaufort.
Pacific Side Warming and Beaufort Break-up
Overall, this Pacific-side warming of the Arctic has driven extent levels back down into the range of 3rd to 4th lowest on record for this time of year. And rapid melt in the Bering, the Sea of Okhost, together with warming in the Beaufort and Hudson Bay may result in new challenges to record lows over the coming days.
By late April, break-up of Beaufort Sea ice is particularly dramatic with very large polynyas forming in a broad region into and north of the Canadian Archipelago and extending on into the off-shore region of the Mackenzie Delta:
(The Beaufort Sea shows extensive break-up and lackadaisical re-freeze on April 26th 2015. Note the extensive dark cracks and polynyas [holes] in the MODIS satellite image above. Such late-spring proliferation of polynyas and cracks can critically reduce albedo as melt season progresses. The Beaufort’s location also makes it vulnerable to continued warm air influx over a very warm Northeastern Pacific Ocean. Image source: LANCE MODIS.)
Temperatures within the Beaufort Sea and near the Canadian Archipelago are still cold enough to support some re-freeze in the Polynya regions. However, closer to the Mackenzie Delta, temps have trended more and more toward near freezing or above freezing levels (sea water freezes at around 28 degrees Fahrenheit). The result is a rather large region with no new ice formation.
More Warm air on the Way
As of 5 PM Eastern Standard time, temperatures in the Mackenzie Delta on the shores of the Beaufort Sea were pushing 32 degrees Fahrenheit. Meanwhile, 50 degree temperatures dominated the region of Great Slave Lake further upstream and southward. These readings are in the range of 8-15 degrees above normal for this time of year, resulting in an early melt pressure for the Mackenzie River and for coastal regions near the post-thaw river outflow zones.
(Big warm-up near the Mackenzie River and through the Northwest Territory in April 28th’s GFS model prediction. Temperatures in the low 70s gather around Great Slave Lake as above freezing temperatures drift down the Mackenzie River reaching all the way to Arctic Ocean Shores. Note near and above sea water freezing temperatures [28 F] throughout the Bering, Beaufort, northwest sections of the Canadian Archipelago and Hudson Bay in the above image. Image source: Earth Nullschool.)
This warm pool is predicted to intensify through tomorrow with temperatures reaching the low 70s Fahrenheit (22 C) near Great Slave Lake and temperatures along Mackenzie Delta shores continuing to edge up over freezing. The warm pool will then linger for another few days before shifting east over Hudson Bay through early next week, pushing temperatures between 10 to 25 degrees Fahrenheit above normal there.
By late next week, long range forecasts show another warm ridge extension through the Mackenzie Delta and melt pressure on the near-shore Beaufort re-intensifying.
Overall, with Arctic Oscillation predicted to remain neutral, melt pressure in the Arctic would tend to reduce somewhat. However, with both Bering and Okhotsk rapidly melting out and with warmth predicted to persist and intensify for those seas as well as for the Beaufort and for Hudson Bay, it appears there’s an even shot that early melt season will proceed at a more brisk than typical pace — again challenging new record lows into early May.