12:45 PM | Global sea ice update...Arctic region gaining considerable ground from a year ago and southern hemisphere at record high for this time of year in terms of areal extent
[Data maps from the Naval Research Laboratory show the change in Arctic ice thickness from one year ago (bottom) to the current levels (top) with a substantial increase]
The southern hemisphere sea ice areal extent continues to run at record highs for today’s date as has been the case for the past couple of weeks using records that go back to 1979 when satellite observations began. In an unusual fashion, the southern hemisphere just recently reached a peak in sea ice areal extent which is a couple of weeks past the normal time of year for this to occur. The southern hemisphere is now heading into their warm season and the areal extent will continue to drop in magnitude.
Meanwhile, the northern hemisphere sea ice areal extent is still running at below normal levels; however, it has increased significantly from last year’s record low amount and its thickness has also grown considerably from one year ago. There have been two distinct trend lines in the northern hemisphere sea ice areal extent dating back to the beginning of satellite era and there seems to be a direct connection with an oceanic cycle in the north Atlantic involving sea surface temperatures. The Arctic region north of the Atlantic Ocean is open to the warmer waters from the south because of the way the ocean currents flow. These warmer waters can flow into the Arctic and prevent sea ice from forming in the North Atlantic. The northern Atlantic Ocean sea surface temperatures are tracked by meteorologists through an index called the Atlantic Multidecadal Oscillation (AMO) and the two distinct trend lines for northern hemisphere sea ice areal extent are quite well correlated with a flip in phases of the AMO in the mid 1990’s from negative (colder water) to positive (warmer water). Specifically, the northern hemisphere sea ice areal extent featured a general sideways trend at above normal levels from 1979 to the mid 1990’s and then, following that flip in the AMO, there has been an overall downward trend to the current below normal values. These oceanic cycles can last for two or three decades and I believe that when the northern Atlantic sea surface temperatures flip back to cooler-than-normal values – perhaps 5 or 10 years from now - the northern hemisphere sea ice areal extent will return to normal or above normal levels - much like it was before the mid 1990’s while the AMO was negative.