Note: Title above is that of NoTricksZone, and not of Kenneth Richard.
Glacier, Ice Sheet Melt Rates Slowing!
By Kenneth Richard
In recent years glacier and ice sheet melt rates have been rapidly decelerating in several regions of the globe.
For illustration only. By Beeblebrox – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11810995
According to published scientific study by Jacob et al. (2012, Recent Contributions of Glaciers and Ice Caps [GIC] to Sea Level Rise), glaciers and ice caps across the world (excluding Greenland and Antarctica) in total only contributed 0.41 mm/yr (~1.6 inches per century) to sea level rise between 2003 and 2010.
This was an overall 30% deceleration from previous year’s estimates, with glaciers in the high mountains of Asia effectively in balance. The abstract states the results are based on a global, simultaneous inversion of monthly GRACE-derived satellite gravity fields, from which the scientists calculate the mass change over all ice-covered regions greater in area than 100 sq km.
The scientists say that the GIC rate for 2003-2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches their study period. Particularly the high mountains of Asia show a mass loss of only 4 ± 20 gigatons per year for 2003-2010, compared with 47-55 Gt yr(-1) in previously published estimates.
Examining Jacob et al. (2012) further, the scientists indicate that the 0.41 mm/yr for 2003-2010 is well less than half the melt rate contribution for the first 5 or 6 years of the 21st century (~0.8 to ~1.1 mm/yr), and even slightly less than the rate for the entire 1961-2004 period (0.4 to 0.5 mm/yr).
The scientists conclude:
Excluding Greenland and Antarctic peripheral GICs [glaciers and ice caps] (PGICs), GICs have variously been reported to have 0.43–0.51 mm yr to sea level rise (SLR) during 1961–2004, 0.77 mm yr during 2001–2004, 1.12 mm yr during 2001–2005 and 0.95 mm yr during 2002–2006.”
Some glaciers have reversed course, and now advancing
Furthermore a recently published (2016) paper indicates that the high mountain glaciers of Asia have actually begun advancing since 2009 (through 2014). A new paper published earlier this year by Zhang, Zhen et al shows similar developments. The scientists state that the glacier mass changes in the Muztag Ata and Kongur Tagh (MAKT) region in the eastern Pamir, northwestern China, is helpful in improving our knowledge of the dynamics of glaciers under a changing climate in High Mountain Asia. They summarize their findings in the paper’s abstract:
Here, glacier area and mass changes derived from remote sensing data are investigated for the period 1971/76–2013/14 for glaciers in MAKT. We have used ASTER images (2013/14), Cartosat-1 (2014) and Landsat, SRTM (Shuttle Radar Terrain Mission) digital elevation model (DEM) (2000), topographic maps (1971/76) and the first and second Chinese glacier inventories (CGIs). Our results indicated that the glacier area of MAKT decreased from 1018.3 ± 12.99 km2 in 1971/ 76 to 999.2 ± 31.22 km2 in 2014 (–1.9 ± 0.2%). Weak area shrinkage of glaciers by 2.5 ± 0.5 km2 (0.2 ± 0.1%) happened after 2000 and the period 2009–2014 even saw a slight expansion by 0.5 ± 0.1 km2 (0.1 ± 0.0%).”
Yet another 2016 paper in the Internal Journal of Quaternary Research authored by a team led by Ireneuzw Sobota indicates that the Aavatsmarkbreen glacier (Svalbard) advanced by over 1 km between 2013 and 2015. The study’s main objective, according to the authors, was to analyse and classify subglacial and supraglacial landforms in the context of glacial deformation and basal sliding over a thin layer of thawed, water-saturated deposits. The study also focused on the geomorphological evidence of surge-related sub- and supraglacial crevassing and glacier front fracturing. The results:
From 2006 to 2013, the average recession of Aavatsmarkbreen was 363 m (52 m a−1). A subsequent surge during 2013–2015 resulted in a substantial advance of the glacier front of over 1 km and an increase in its surface area of more than 2 sq. km.”
This rapid regional (Arctic) glacier expansion since 2013 coincides with Greenland’s recent ice sheet melt deceleration. According to the Arctic Report Card (2015), after losing an average of ~260 Gt per year from 2002 to 2013, ice sheet losses decelerated to -29 gigatons and -186 gigatons in 2013-14 and 2014-15 respectively.
The ice mass loss of 186 Gt over the entire ice sheet between April 2014 and April 2015 was 22% below the average mass loss of 238 Gt for the 2002- 2015 period, but was 6.4 times higher than the 29 Gt loss of the preceding 2013-2014 season. They add:
The net area loss from marine-terminating glaciers during 2014-2015 was 16.5 sq km.. This was the lowest annual net area loss of the period of observations (1999-2015) and 7.7 times lower than the annual average area change trend of -127 sq km.”
And, already for 2016, the surface mass balance (see graph below, blue trend line) is well above the 1990-2013 mean, marking the third straight year of Greenland ice sheet melt deceleration.