(Image source: Uni Bremen)
The most recent updates from the Japanese Space Agency (JAXA) and Uni Bremen show Arctic sea ice extent in very rapid early season decline. The above graph, produced by Uni Bremen, shows a stunning loss of sea ice extent over the past week of more than 1 million square kilometers. Such extent losses are almost unheard of for this time of year, with retraction, at least according to Uni Bremen, even out-pacing what is usual for July and August.
Uni Bremen is not the only sea ice extent monitor and not all the others show such a rapid decline. Uni Bremen uses less smoothing, so we will expect to see whether these numbers bear out in the other measures over the coming days. Ominously, JAXA is also showing a rapid extent decline:
(Image source: JAXA)
Though neither as extensive nor as sudden as Uni-Bremen losses, the JAXA graph does show a rapid decline of about 500,000 square kilometers over the past week. NSIDC and DMI, on the other hand, show declines to be much more gradual. The NSIDC area measurement also is currently showing a much more gradual decline.
As noted above, the discrepancy between these measures should wash out over the next week. But early indications from JAXA and Uni-Bremen are some cause for concern.
Conditions in Context
Arctic conditions in context show warmer than average air temperatures remaining over much of the region. These departures from normal high and low temperatures are not as great as they were a week ago. However, these warmer than normal air temperatures are also now riding on top of a seasonal increase and so more rapidly push the Arctic toward melting.
Warmer than average water temperatures also continue to pervade over most of the Arctic Ocean. Recent reports have confirmed sporadic warm water upwelling throughout the Arctic. These events contribute to bottom melt and cracking of sea ice and are just one more mechanism pushing the Arctic sea ice into decline. Such warm water upwelling is likely linked to a rapid increase in ocean heat content. A portion of this newly sequestered heat energy appears to already have done quite a bit of work in reducing Arctic sea ice extent, area and volume. One such upwelling event occurred off Barrow Alaska in March of 2013. The event combined with off-shore winds to result in ice free waters for a short time off Barrow, one of the consistently coldest locations in the Northern hemisphere, in winter time. Such events have been known to occur. But the up-welling and wind driven melt this March was one of the largest such winter-time events yet witnessed and it coincided with an immense sea ice cracking event.
(Image source: Uni-Koeln)
Overall, we see warm air temperatures over Eastern Europe and Russia rapidly expanding northward with above freezing temperatures crossing the Arctic Circle in some areas. Even Siberia is seeing rapidly warming temperatures. Cooler air remains settled in over Greenland and the Canadian Arctic Archipelago (CAA). These conditions are somewhat the reverse of those seen earlier in the month when Greenland and Baffin Bay showed warmer temperatures while Europe and Russia shivered.
As the Arctic continues to warm, we are likely to see sea ice melt continue at a slow to moderate pace. That said, an increasing number of indicators show the potential (low to moderate) for a major pick-up in early season melt rates come late April/early May. Should these events emerge, the upshot would be the possible start to a summer of massive Arctic melt. A melt that would be the pre-cursor or possibly even the start of a new period of ice-free or near ice-free summers. It is still too soon to make this call. That said, it is possible we are seeing some foreshadowing in the Uni-Bremen and JAXA measures showing very rapid extent losses over the past week.
As a final note, it important to re-iterate that the Arctic sea ice remains extraordinarily thin, fractured and fragile for this time of year with continued rumblings that melt may begin to proceed rapidly and well ahead of schedule.
Uni-Bremen has just posted a revised estimate of sea ice extent. This revision shows melt occurring at a somewhat more gradual pace. You can view the revised data here. JAXA estimates, however, remain the same as previously posted.