It doesn’t take much to shove Arctic sea ice toward new record low values these days. Human caused climate change has made it easy for all kinds of weather systems to bully the ice.
In the case of the past seven days, three moderate strength high pressure cells churned away over the central Arctic, bringing with them clear skies, air temperatures in the range of average for 1979-2000 above the 70 North Latitude line, and a clockwise circulation favoring sea ice compaction and warm water upwelling at the ice edge.
The highs measured in the range of 1020 to 1025 hPa barometric pressure. Moderate-strength weather conditions that during a typical year of the last century would have been almost completely non-noteworthy. Today, instead, we have sea ice extent testing new record lows in the Japanese Space Agency’s monitor:
(Arctic sea ice extent as recorded by JAXA. Image source: IJIS Sea Ice Monitor.)
On June 30, JAXA showed Arctic Sea Ice extent totals in the range of 9,058,000 square kilometers or approximately tied with previous all-time record lows for the date set in 2011 and 2012. By comparison, NSIDC showed extent plunging to 3rd lowest in the record on June 29th and remaining in the same range on June 30th.
Weak Ice Facing Warm Winters, Hot Water
So how can moderate weather systems have such a powerful effect on sea ice? One need only look back to this winter when Arctic temperatures surged to 5-7 C above average for months on end with large areas experiencing extended periods of + 20 C above average readings. An extraordinary and abnormal warmth in winter that harms sea ice resiliency during summer periods of above freezing temperatures and 24 hour daylight.
In addition, sea surface temperatures in the Arctic are very warm. Much, much warmer than during similar periods of the 20th Century. The ice edge is surrounded on all sides by water that is much hotter than normal and even warmer waters lurk in the Arctic depths, waiting for only the slightest weather disturbance to dredge it to the surface. In this case, Arctic high pressure systems result in warm water upwelling at the ice edge, exactly where the ice is weakest.
(Arctic Sea Surface temperature Anomaly showing much hotter than normal water temperatures throughout the Arctic on June 30, 2014. Image source: NOAA/National Weather Service.)
The above graphic provides a stark view of how hot Arctic Ocean waters have now become with most ice edge zones seeing temperatures in the range of 2.25 to even 8+ C values. This heat pressure combines with the ongoing ocean mixing and clear skies influence of even moderate high pressure systems to challenge sea ice record lows set just 2-3 years ago.
GFS model runs show high pressure systems continuing to dominate the Central Arctic for at least the next 144 hours. After that time, warm storms are shown to encroach over the Chukchi and East Siberian Seas. Throughout that time, solar insolation will continue to proliferate melt ponds over the sea ice even as warm water up-wells at the ice edge and the moderate strength high pressure domes continue to compact the ice.
(Arctic sea ice on June 30, 2014 as viewed from NASA’s LANCE MODIS sensor array showing a sea ice extent that is, in some measures, currently tied with record lows set in 2011 and 2012. Note the very large open areas of dark water in the Laptev, the Beaufort and Chukchi Seas. These regions have been particularly vulnerable to rapid recession in 2014. In addition, note the characteristic blue tint of some ice sections in the image, indicating melt pond formation over large regions under the influence of high pressure and related clear skies.)
Given current trends, it appears we have about a 50-50 shot of seeing new record lows in some measures by the end of this melt season. Under the massive overall stress delivered to the Arctic sea ice by a combination of factors directly attributable to human-caused warming, it appears possible that near zero sea ice conditions may emerge one summer between now and 2020. Finally, with sea ice measures falling between 50-80 percent below 1979 levels over recent years, the overall stress to global and Northern Hemisphere weather systems has become quite extreme. A trend, unfortunately, that is bound to continue so long as human carbon emissions and related amplifying feedbacks remain at extraordinarily dangerous levels.