UPDATE: A newer post on Antarctica points out that there is a volcanic chain running under or near the parts of Antarctica that are warming or melting. The scientists and media forgot to mention…
The new-old scare is Antarctica and what a messy situation it is. Only two weeks ago Matthew England was saying that Ocean winds were keeping Antarctica cool, and that Antarctica was stealing Australian rain.
Now a new Cryosat study by Malcolm McMillan et al is generating headlines saying that Antarctic ice is “disappearing at twice the rate predicted”. (Can someone calculate the date it will be all gone?)
Well, at least it’s worse now than it was all of three years ago when the new Cryosat data first started.
Now they finally can record “near continuous 96% coverage of the continent”, with “a fivefold increase in the sampling of coastal regions where the vast majority of all ice losses occur.” It’s good that we have better data, but these are very short trends. Who’s leaping to hit the panic button? If there is message here it’s that ice loss is a complicated beast; it isn’t just about temperature, but also about precipitation, ablation, and wind which vary a lot. Other studies that are 791 years longer suggest the Antarctic action lately is nothing unusual.
Cryosat shows (probably) that West Antarctica is losing ice at a rate of −134 ± 27 Gt per year. But East Antarctica is somehow showing no signs of melting, despite record Chinese emissions, “losing ice” at −3 ± 36 Gt per year (that’s somewhere between a loss of 39Gt a year or a gain of 33Gt a year). The Antarctic Peninsula, which was warming ten times faster than the rest of the world, is melting somewhat: at −23 ± 18 Gt per year. I see The Guardian says the ice loss applies to all of Antarctica. They never were that good with numbers.
McMillan go on to conclude that the melting Antarctic is causing a sea level rise since 2010, of0.45 ± 0.14 mm per year. Here’s a strange implication though. McMillan doesn’t mention the missing heat, but by definition if Antarctica is causing more sea level rise, then the missing heat in the deep abyss is doing less. Has it all gone to West Antarctica?
The material thing here is that the predictions may have changed, but the seas are not rising any faster than they were before the press release. What has changed (possibly) is our knowledge of the cause of the rise. West Antarctica might well be losing ice and raising sea levels, but since sea levels have sea-levels have decelerated since 2004, this begs the question (even more than it was already being begged) of where the missing heat in the ocean went that was supposed to be causing thermal sea level rise? This would mean there is even less sea level rise due to the so-called missing heat? As I warned two weeks ago: “…attributing sea level changes 2 kilometers down to “missing heat” from a trace gas 10 kilometers up is “not obvious”. Occams razor on Vodka.“
When trends are so short the claims that it’s “twice as fast” as they thought are pure hype. Why don’t they also mention that sea levels are not rising as fast as they thought? Where are those headlines, like “Missing Ocean Heat Causes Much Lower Sea-level Rise than Predicted!”. “Scientists Fears on Ocean Warming
The mystery of ice, ice sheets, melting and no-warming
As we see in these latest graphs below, somehow there is more sea ice around Antarctica, and temperatures are not warming over most of Antarctica either. Yet the missing heat has apparently gone to the West Antarctic sheet.
Paul Homewood has some nice alternate graphs on this. This covers quite a lot of Antarctica. Damn sneaky heat. There is pretty much no warming trend, though a slight recovery to former temperatures might be melting some ice that formed in the early 1980s. How significant is a trend that starts in 2005?
We use 3 years of Cryosat-2 radar altimeter data to develop the first comprehensive assessment of Antarctic ice sheet elevation change. This new dataset provides near-continuous (96%) coverage of the entire continent, extending to within 215 kilometres of the South Pole and leading to a fivefold increase in the sampling of coastal regions where the vast majority of all ice losses occur. Between 2010 and 2013, West Antarctica, East Antarctica, and the Antarctic Peninsula changed in mass by −134 ± 27, −3 ± 36, and −23 ± 18 Gt yr−1 respectively. In West Antarctica, signals of imbalance are present in areas that were poorly surveyed by past missions, contributing additional losses that bring altimeter observations closer to estimates based on other geodetic techniques. However, the average rate of ice thinning in West Antarctica has also continued to rise, and mass losses from this sector are now 31% greater than over the period 2005–2011.
We estimate that, since 2010, the average Antarctic ice sheet contribution to global sea level rise has been 0.45 ± 0.14 mm yr-1. This value, which is more than twice as large as the 20-year mean determined from an ensemble of geodetic techniques (0.19 ± 0.15 mm yr-1 Acknowledgements in Shepherd et al., 2012), reflects both the improved capability of CryoSat-2 to observe regions of ice dynamical imbalance, and the impact of short- and intermediate-term changes in ice sheet mass. In West Antarctica, there is now little doubt that the rate of ice loss has continued to rise, and that, with over 97 % sampling of this region, this increase is now well-resolved. However, in East Antarctica and at the Antarctic Peninsula, the average change in ice sheet mass remains small in comparison to expected fluctuations in snow accumulation (Table 1), which present an observational challenge to all geodetic techniques. Although the CryoSat-2 measurements allow an improved understanding of the drivers and timescales of ice sheet imbalance in these sectors, longer-period data sets are required to separate the effects of meteorological and ice dynamical imbalance [Wouters et al., 2013]. Nevertheless, the fine spatial and temporal resolution of ice sheet elevation changes afforded by interferometric synthetic aperture radar altimetry represents a remarkable advance on the capability of past missions, and provides greater confidence in assessments of ice sheet mass imbalance.
WAIS Divide Project Members, (2013) Onset of deglacial warming in West Antarctica driven by local orbital forcing, Nature, 500, 440–444 doi:10.1038/nature12376