Current State of the Sea Ice Cover

The data is getting better.   We have essentially lost half of our perennial sea ice since 1978.  The actual cover is mostly caused by annual ice and this feeds the natural reservoir provided by the perennial ice.  All this suggests that present trends will eliminate perennial ice by 2050 while annual cover will substantially contract.

It should be stable at that point.

We do not have good enough data to say when and how reversals take place.  Recall that the Medieval warm period lasted centuries.  This feels like the same scenario is working through.  Not quite ever blue water, but navigable enough for the prepared.  Certainly the Vikings took advantage of it back then.

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Current State of the Sea Ice Cover

J. C. Comiso, C. L. Parkinson, T. Markus, D. J. Cavalieri and R. Gersten

http://neptune.gsfc.nasa.gov/csb/index.php?section=234

The sea ice cover is one of the key components of the climate system. It has been a focus of attention in recent years, largely because of a strong decrease in the Arctic sea ice cover and modeling results that indicate that global warming could be amplified in the region by a factor of about 3 to 5 times on account of ice-albedo feedback. This results from the high reflectivity (albedo) of the sea ice compared to ice-free waters. A satellite-based data record starting in late 1978 shows that indeed rapid changes have been occurring in the Arctic, where the perennial ice cover has been declining at the rate of about 13% per decade and the ice cover as a whole has been declining at the lesser rate of about 5% per decade. In the Antarctic, the trend is opposite to that in the Arctic, with the sea ice cover increasing at about 1 to 2 % per decade. This is despite unusual warming in the Antarctic Peninsula region and declines in the sea ice cover in the Amundsen/Bellingshausen Seas of about 6% per decade. In the Arctic, a slight recovery in the sea ice cover has been observed in 2008 and 2009, following a major decline of the ice in 2007, while in the Antarctic, the sea ice cover was more extensive than normal in 2007, 2008, and 2009. Shown below are up-to-date satellite observations of the sea ice covers of both the Arctic and the Antarctic, along with comparisons with the historical satellite record of more than 30 years. The plots and color coded maps are chosen to provide information about the current state of the sea ice cover and how the most current daily data available compare with the record lows and record highs for the same date during the satellite era.

Figure 1: 10-year averages between 1979 and 2008 and yearly averages for 2007, 2012, and 2016 of the daily (a) ice extent and (b) ice area in the Northern Hemisphere and a listing of the extent and area of the current, historical mean, minimum, and maximum values in km2.

Figure 2: Color-coded map of the daily sea ice concentration in the Northern Hemisphere for the indicated recent date along with the contours of the 15% edge during the years with the least extent of ice (in red) and the greatest extent of ice (in yellow) during the period from November 1978 to the present. The extents in km2 for the current and for the years of minimum and maximum extents are provided below the image. The different shades of gray over land indicate the land elevation with the lightest gray being the highest elevation.

Figure 3: 10-year averages between 1979 and 2008 and yearly averages for 2012, 2014, and 2016 of the daily (a) ice extent and (b) ice area in the Southern Hemisphere and a listing of the extent and area of the current, historical mean, minimum, and maximum values in km2.

Figure 4: Color-coded map of the daily sea ice concentration in the Southern Hemisphere for the indicated recent date along with the contours of the 15% edge during the years with the least extent of ice (in red) and the greatest extent of ice (in yellow) during the period from November 1978 to the present. The extents in km2 for the current and for the years of minimum and maximum extents are provided below the image. The different shades of gray over land indicate the land elevation with the lightest gray being the highest elevation.

Figure 5. Seasonal cycle of Northern Hemisphere sea ice extents (a) and areas (b), given as daily averages, for the years 2007 through 2016. The vertical line represents the last data point plotted.

Figure 6. Seasonal cycle of Southern Hemisphere sea ice extents (a) and areas (b), given as daily averages, for the years 2007 through 2016. The vertical line represents the last data point plotted.