Someone triggered Antarctica for this week’s media alarm blitz.
Antarctic ice loss increases to 200 billion tonnes a year – Climate Action
Antarctica is now melting three times faster than ever before – Euronews
Antarctica is shedding ice at an accelerating rate – Digital Journal
Al Gore Sounds the Alarm on 0.3 inches of Sea Level Rise from Ice Sheets– Daily Caller
Antarctica is losing an insane amount of ice. Nothing about this is good. – Fox News
Looks like it’s time yet again to play Climate Whack-A-Mole. That means stepping back to get some perspective on the reports and the interpretations applied by those invested in alarmism.
The Antarctic Ice Sheet extends almost 14 million square kilometers (5.4 million square miles), roughly the area of the contiguous United States and Mexico combined. The Antarctic Ice Sheet contains 30 million cubic kilometers (7.2 million cubic miles) of ice. (Source: NSIDC: Quick Facts Ice Sheets)
The Antarctic Ice Sheet covers an area larger than the U.S. and Mexico combined. This photo shows Mt. Erebus rising above the ice-covered continent. Credit: Ted Scambos & Rob Bauer, NSIDC
The study of ice sheet mass balance underwent two major advances, one during the early 1990s, and again early in the 2000s. At the beginning of the 1990s, scientists were unsure of the sign (positive or negative) of the mass balance of Greenland or Antarctica, and knew only that it could not be changing rapidly relative to the size of the ice sheet.
Advances in glacier ice flow mapping using repeat satellite images, and later using interferometric synthetic aperture radar SAR methods, facilitated the mass budget approach, although this still requires an estimate of snow input and a cross-section of the glacier as it flows out from the continent and becomes floating ice. Satellite radar altimetry mapping and change detection, developed in the early to mid-1990s allowed the research community to finally extract reliable quantitative information regarding the overall growth or reduction of the volume of the ice sheets.
By 2002, publications were able to report that both large ice sheets were losing mass (Rignot and Thomas 2002). Then in 2003 the launch of two new satellites, ICESat and GRACE, led to vast improvements in one of the methods for mass balance determination, volume change, and introduced the ability to conduct gravimetric measurements of ice sheet mass over time. The gravimetric method helped to resolve remaining questions about how and where the ice sheets were losing mass. With this third method, and with continued evolution of mass budget and geodetic methods it was shown that the ice sheets were in fact losing mass at an accelerating rate by the end of the 2000s (Veliconga 2009, Rignot et al. 2011b).
A new 2015 NASA study says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.
The research challenges the conclusions of other studies, including the Intergovernmental Panel on Climate Change’s (IPCC) 2013 report, which says that Antarctica is overall losing land ice.
According to the new analysis of satellite data, the Antarctic ice sheet showed a net gain of 112 billion tons of ice a year from 1992 to 2001. That net gain slowed to 82 billion tons of ice per year between 2003 and 2008.
“We’re essentially in agreement with other studies that show an increase in ice discharge in the Antarctic Peninsula and the Thwaites and Pine Island region of West Antarctica,” said Jay Zwally, a glaciologist with NASA Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study, which was published on Oct. 30 in the Journal of Glaciology. “Our main disagreement is for East Antarctica and the interior of West Antarctica – there, we see an ice gain that exceeds the losses in the other areas.” Zwally added that his team “measured small height changes over large areas, as well as the large changes observed over smaller areas.”
Scientists calculate how much the ice sheet is growing or shrinking from the changes in surface height that are measured by the satellite altimeters. In locations where the amount of new snowfall accumulating on an ice sheet is not equal to the ice flow downward and outward to the ocean, the surface height changes and the ice-sheet mass grows or shrinks.
Snow covering Antarctic peninsula.
Keeping Things in Perspective
Such reports often include scary graphs like this one and the reader is usually provided no frame of reference or context to interpret the image. First, the chart is showing cumulative loss of mass arising from an average rate of 100 Gt lost per year since 2002. Many years had gains, including 2002, and the cumulative loss went below zero only in 2006. Also, various methods of measuring and analyzing give different results, as indicated by the earlier section.
Most important is understanding the fluxes in proportion to the Antarctic Ice Sheet. Let’s do the math. Above it was stated Antarctica contains ~30 million cubic kilometers of ice volume. One km3 of water is 1 billion cubic meters and weighs 1 billion tonnes, or 1 gigatonne. So Antarctica has about 30,000,000 gigatonnes of ice. Since ice is slightly less dense than water, the total should be adjusted by 0.92 for an estimate of 27.6 M Gts of ice comprising the Antarctic Ice Sheet.
So in the recent decade, an average year went from 27,600,100 Gt to 27,600,000, according to one analysis. Other studies range from losing 200 Gt/yr to gaining 100 Gt/yr.
Even if Antarctica lost 200 Gt/yr. for the next 1000 years, it would only approach 1% of the ice sheet.
If like Al Gore you are concerned about sea level rise, that calculation starts with the ocean area estimated to be 3.618 x 10^8 km2 (361,800,000 km2). To raise that area 1 mm requires 3.618×10^2 km3 or 361.8 km3 water (1 km3 water=1 Gt.) So 200 Gt./yr is about 0.55mm/yr or 6 mm a decade, or 6 cm/century.
By all means let’s pay attention to things changing in our world, but let’s also notice the scale of the reality and not make mountains out of molehills.
Let’s also respect the scientists who study glaciers and their subtle movements over time (“glacial pace”). Below is an amazing video showing the challenges and the beauty of working on Greenland Glacier.
For more on the Joys of Playing Climate Whack-A-Mole