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

The sea ice cover is one of the key components of the polar 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 Arctic 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 ice coverage has been declining at a substantial rate. In contrast, in the Antarctic the sea ice coverage has been increasing although at a lesser rate than the decreases in the Arctic. 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 37 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. Sea ice concentration is the percent areal coverage of ice within the data element (grid cell). Sea ice extent is the integral sum of the areas of all grid cells with at least 15% ice concentration, while sea ice area is the integral sum of the product of ice concentration and area of all grid cells with at least 15% ice concentration. The dashed vertical line indicates the date of the latest plotted and mapped data.

Figure 1: 10-year averages between 1979 and 2018 and yearly averages for 2007, 2012, and 2020 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. Seasonal cycle of Northern Hemisphere sea ice extents (a) and areas (b), given as daily averages, for the years 2010 through 2020. The vertical line represents the last data point plotted.

Figure 4: Color-coded animation displaying the last 2 weeks of the daily sea ice concentrations in the Northern Hemisphere. These images use data from the AMSR-E/AMSR2 Unified Level-3 12.5 km product. The different shades of gray over land indicate the land elevation with the lightest gray being the highest elevation.

Figure 5: 10-year averages between 1979 and 2018 and yearly averages for 2012, 2014, and 2020 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 6: 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 7. Seasonal cycle of Southern Hemisphere sea ice extents (a) and areas (b), given as daily averages, for the years 2010 through 2020. The vertical line represents the last data point plotted.

Figure 8: Color-coded animation displaying the last 2 weeks of the daily sea ice concentrations in the Southern Hemisphere. These images use data from the AMSR-E/AMSR2 Unified Level-3 12.5 km product. The different shades of gray over land indicate the land elevation with the lightest gray being the highest elevation.