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THIS POST IS A CRITICAL REVIEW OF A MEDIA REPORT [LINK] IN MAY 2020 THAT NASA SATELLITES RECORDED AN ALARMING RATE OF ICE MELT IN GREENLAND AND ANTARCTICA 2003-2019 THAT CAUSED 14 MM OF SEA LEVEL RISE. THE MEDIA IS REPORTING FINDINGS FROM AN AAAS SCIENCE JOURNAL ARTICLE [LINK] .  THE CITATION AND ABSTRACT APPEAR BELOW.

WHAT THE RESEARCH PAPER SAYS

Ben Smith etal, Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes . Abstract: Quantifying changes in Earth’s ice sheets, and identifying the climate drivers, is central to improving sea-level projections. We provide unified estimates of grounded and floating ice mass change from 2003 to 2019 using NASA’s ICESat and ICESat-2 satellite laser altimetry. Our data reveal patterns likely linked to competing climate processes: Ice loss from coastal Greenland (increased surface melt), Antarctic ice shelves (increased ocean melting), and Greenland and Antarctic outlet glaciers (dynamic response to ocean melting), was partially compensated by mass gains over ice sheet interiors (increased snow accumulation). Losses outpaced gains, with grounded-ice loss from Greenland (200 Gt a⁻¹) and Antarctica (118 Gt a⁻¹) contributing 14 mm to sea level. Mass lost from West Antarctica’s ice shelves accounted for over 30% of that region’s total.

WHAT THE MEDIA REPORT SAYS 

HEADLINE: NASA satellites bearing advanced laser technology have recorded the most accurate picture of large scale ice sheet melting in Greenland and Antarctica to date. Key points: (1) NASA satellites help scientists track Greenland and Antarctica’s contribution to sea level rise. (2) Melting Antarctic ice shelves lead to glaciers flowing into the sea.  (3) Melting ice sheets in Greenland and Antarctica contributed to 14mm of sea level rise between 2003 and 2019, according to a study published today in the journal Science.

ABBREVIATED TEXT OF THE ARTICLE:  (The full text is available here  [LINK]

1. Overview: With that 14 millimetres of sea level rise every 16 years, it adds up to a pretty significant amount of sea level rise. Two satellites, the ICESat-1 and the more advanced ICESat-2, were equipped with “laser altimeters that bounced light pulses off the ice sheets to determine their height. Researchers compared measurements taken in the early 2000s by ICESat-1 with measurements taken in 2018 and 2019 by ICESat-2. The two sets of measurements intersect each other at millions of points and those intersections are used to map how the ice changed between ICESat-1 and ICESat-2. This is a much more significant climatic signal than what you might see if you just surveyed for two or three years.
2. Greenland vs Antarctica: Previous satellite data from NASA show the rate of global mean sea level rise is accelerating by an average of 3.4 millimetres per year per year. Melting ice from Greenland and Antarctica contributes to about a third of the sea level rise we’re seeing. The latest data showed melting was more extreme in Greenland than in Antarctica. Greenland’s ice sheet lost an average of 200 gigatons of ice a year, contributing up to two thirds of the sea level rise.
3. AGW Climate Change Causes the Ice Melt: The majority of this ice loss was from thinning of coastal glaciers, which have been impacted by warmer summer temperatures melting the ice on the surface, and warmer ocean temperatures eroding the edges of the ice. Greenland melts at the surface quite a bit every year whereas the surface of Antarctica does not melt over a significantly large areas of the continent. Antarctica lost 118 gigatons of ice in that time period. While there are gains in ice coverage in the interior due to increased snowfall, these did not outweigh the losses in coastal areas. The total amount of thinning vastly outweighs the small amount of thickening in the interior of the ice sheets.
4. The majority of Antarctica’s contribution to sea level rise comes from its glaciers flowing into the ocean as warmer water erodes the ice. This process is far more rapid in West Antarctica than in East Antarctica where it is quite patchy, with areas of thickening and thinning. The satellite data shows both grounded ice such as glaciers and land ice extending onto the sea, whereas previous studies focused on just one or the other. We know that ice on land responds to ice extending onto the sea, so looking at the ice sheet as a whole is an advantage.
5. Antarctic Ice Shelves:  The scientists discovered that where grounded ice changes most is where the ice shelves are thinning. While ice shelves, which float on the ocean, don’t contribute to sea level rise, they act like a barrier, anchoring glaciers on the Antarctic landmass. Antarctica functions a bit like a giant apple pie, when the crust is removed, the filling leaks out.

CRITICAL COMMENTARY

The paper finds that in the 17-year study period 2003-2019, Greenland lost 200 gigatonnes of ice per year on average. In a related post [LINK] , we used the IMBIE team’s mass balance data for Greenland for the period  1992-2019 along with surface melt data provided by NSIDC and found that Greenland lost on average 151 gigatonnes per year in that 28-year period and that the mass balance time series and UAH lower troposphere temperature time series for that region are correlated. These data provide support for the assumed global warming causation hypothesis. The evidence is consistent with the proposition that atmospheric warming above the Arctic had caused the ice melt.

For Antarctica the paper finds that in the 17-year study period 2003-2019 the West Antarctic Ice Sheet (WAIS) inclusive of the Antarctic Peninsula lost on average 245 gigatonnes per year but that the East Antarctic Ice Sheet (EAIS) gained 196 gigatonnes per year on average. The net loss for Antarctica appears to be a mere 49 gigatonnes per year equal to the uncertainty range of the WAIS loss estimated in this study as +/- 49 gigatonnes per year. The peculiar geographical distribution of ice melt in Antarctica does not support an atmospheric cause by way of fossil fuel driven global warming but in fact, the melt geography exactly matches the geological features of West Antarctica and the Antarctic Peninsula such that the melt can be explained in terms of geothermal heat. The relevant geological features of West Antarctica including the Antarctic Peninsula include the West Antarctic Rift system and the Marie Byrd Mantle Plume described in a related post on this site [LINK] . Analysis of Antarctic ice melt in terms of these geological features are provided in other posts on this site listed below. 

1. ANTARCTICA THREATENS TO FLOOD FLORIDA [LINK]
2. WEST ANTARCTIC ICE SHEET COLLAPSE [LINK]
3. WEST ANTARCTIC GLACIERS ARE DOOMED [LINK]
4. FOSSIL FUELS MELTING ANTARCTICA [LINK]

CONCLUSION: SATELLITE ALTIMETRY DATA MAY PROVIDE ACCURATE MEASURES OF ICE LOSS BUT THEY DO NOT PROVIDE CAUSATION INFORMATION. THE REASON FOR THE MELT MUST BE INVESTIGATED INDEPENDENTLY AND NOT SIMPLY ASSUMED TO BE DRIVEN BY AGW CLIMATE CHANGE SUCH THAT THE OBSERVED MELT RATE CAN BE ATTENUATED WITH CLIMATE ACTION IN THE FORM OF REDUCING FOSSIL FUEL EMISSIONS.