From the NSIDC
June 26, 2021
Surface melt and the total melt area of the Greenland ice sheet at the end of the spring 2021 season were below the 1981-2010 average. Snowfall and rain (minus runoff) added bulk to the ice sheet. On June 20, the total mass gain of the ice sheet since September 2020 was slightly above average. The tip from June 25th to June 27th will be discussed in a later post.
Overview of the conditions
Figure 1. The top left map of the Greenland ice sheet shows the total number of melting days through June 20 this year. The top right map shows the difference between the total melting days in 2021 from January 1 to June 20 and the number of average melting days from 1981 to 2010 for the same period. The graph below shows the daily area in square kilometers of surface melt from April 1 to June 20, 2021, with daily trends in melt expansion for the previous five years.
Source: National Snow and Ice Data Center / T. Mote, University of Georgia
High resolution image
The total air expansion of the surface melt (total expansion on the melting day) up to June 20 was just over 2.49 million square kilometers (961,000 square miles), 1.5 times below the average from 1981 to 2010 of 3.72 million square kilometers (1, 44 million square miles). Melting was slightly below average along the west-central ice sheet and significantly below average on the south-western edge of the ice sheet (10 to 12 days below average speed). Limited areas in the north and northwest had slightly above average melts, but the overall extent of these areas was small.
Conditions in context
Figure 2. The upper diagram shows the air temperature as the difference to the average in relation to 1981 to 2010 for the period from May 1 to June 20, 2021 in degrees Celsius. The diagram below shows the difference in altitude from the average in meters for the 700 millibar pressure level in the atmosphere for the same period.
Source: National Centers for Environmental Prediction (NCEP) Reanalysis data, National Center for Atmospheric Research
High resolution image
The average air temperature at 700 millibars (about 10,000 feet) and the average altitude at 700 millibars (a measure of air pressure) summarize spring weather conditions. Air temperatures over Greenland varied across the ice sheet, with warm conditions in the northwest and cool conditions in the southeast. The region near Thule in the northwest was more than 2 degrees Celsius (4 degrees Fahrenheit) above the 1981-2010 average, while conditions near the great Helheim Glacier in the southeast were about 2 degrees Celsius (4 degrees Fahrenheit) below average lay.
Atmospheric pressure patterns, indicated by the altitude above the average of the 700 millibar level (about 10,000 feet above the ground, but higher under high pressure conditions and lower under low air pressure) show an area of moderate high pressure in the northwest of the island and low pressure over the Irminger Sea between Greenland and Iceland.
Greenland is covered in snow
Figure 3a. This graph shows the surface mass balance (SMB) estimates for the Greenland Ice Sheet for the spring 2020 season from autumn to 2021 (red line) to 30 average. Some of the last few years are also included for comparison. SMB is the sum of snowfall and precipitation minus evaporation or runoff. The estimates come from the MARv3.11 model, which is based on daily weather measurements and projections.
Source: Amory et al. 2021, MARv3.11, Xavier Fettweis, University of Liège, Belgium
High resolution image
Figure 3b. The top left map shows the total surface mass balance (SMB) over Greenland from September 1, 2020 to June 20, 2021. The top right map shows the difference between the 1981 and 2010 average in centimeters of water equivalent. Below is an image of the west-central area of the Greenland Ice Sheet, taken on June 21, 2021, showing a persistent blanket of snow over the ice sheet’s broken ice.
Photo credit: Amory et al., 2021
Photo credit: Jason Box, Geological Survey of Denmark and Greenland (GEUS)
High resolution image
On June 20, the total surface mass balance of the ice sheet was around 550 billion tons, slightly above the average of the total input of snow and rain since September 2020, 41 billion tons more than the average (Figure 3a).
The total snowfall was slightly above average for the ice sheet. Areas that received additional snow that year were in the southeast, where some areas had 50 to 70 centimeters (20 to 28 inches) more snow water equivalent than average, and to a lesser extent along the west coast (Figure 3b). Large areas of the central and northeastern ice sheet have been almost average over the year to date.
The surface mass balance above the ice sheet from September 1, 2020 to June 20, 2021 was around 8 percent above the average from 1981 to 2010, with 7 percent above-average snowfall and 10 percent below-average melt runoff.
Greenland is covered in snow
Figure 3a. This graph shows the surface mass balance (SMB) estimates for the Greenland Ice Sheet for the spring 2020 season from autumn to 2021 (red line) to 30 average. Some of the last few years are also included for comparison. SMB is the sum of snowfall and precipitation minus evaporation or runoff. The estimates come from the MARv3.11 model, which is based on daily weather measurements and projections.
Source: Amory et al. 2021, MARv3.11, Xavier Fettweis, University of Liège, Belgium
High resolution image Figure 3b. The top left map shows the total surface mass balance (SMB) over Greenland from September 1, 2020 to June 20, 2021. The top right map shows the difference between the 1981 and 2010 average in centimeters of water equivalent. Below is an image of the west-central area of the Greenland Ice Sheet, taken on June 21, 2021, showing a persistent blanket of snow over the ice sheet’s broken ice.
Photo credit: Amory et al., 2021
Photo credit: Jason Box, Geological Survey of Denmark and Greenland (GEUS)
High resolution image
You can find the full article here.
HT / Renee H.
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