How do you measure ice loss in Antarctica?

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by Emil Morhardt

In a new paper about accelerated ice loss in Antarctica, Rignot et al. (2019) list the three ways: 1. the component method in which whatever data on ice and snow amounts are available at the finest resolution possible, from the smallest areas studied areas (as little as 100 meters, ranging up to 1km) are collected then added up for as many years as they are available, and the trend plotted; 2. The altimetry method which, I presume, uses satellite altimetry to figure out how much ice and snow are present based on the height above ground and sea is measured…this has a spatial resolution of 1-10km; and 3.  The gravity method (probably using the Grace satellite pairs to measure gravity changes over time owing to ice loss. The latter method can resolve centimeter-level losses but at a low resolution of 333 km. The latter two methods are relatively easy…just process satellite data…or maybe not so easy but relatively so. The component method is labor intensive, but better at pinpointing areas of loss which facilitates trying to understand what is causing the loss. Rignot used the component method.

Their results, reported widely in the news media, should be chilling.  The climate-change enhanced westerly winds in the southern hemisphere are evidently pushing relatively warm circumpolar deep water (CDW) up against the edges of the ice sheets over much of the continent and increasing their melting and calving of icebergs at much higher rates than in previous decades. The loss of ice not only increases sea level faster than anyone had thought, it allows glaciers to flow into the sea faster as well, speeding the whole process.

Not that this comes as too much of a surprise to those of us who have been following global warming, but considering the exacerbated coastal flooding that is becoming commonplace, it might be good to point out to the climate change deniers inhabiting the higher levels of our government.

Rignot et al. 2019, http://www.pnas.org/cgi/doi/10.1073/pnas.1812883116

Very Large Wildland Fires Predicted to Increase in Rocky Mountains and Pacific Northwest

by Emil Morhardt

In the middle of one of the worst fire seasons on record for Northern California comes a new modeling paper by scientists at CalTech’s Jet Propulsion Laboratory, the University of Idaho, and the US Forest Service Pacific Wildland Fire Sciences Laboratory predicting no effect of climate change on Northern California Very Large Wildfires (VLWFs), but potentially large increases in them in the Pacific Northwest and Rocky Mountains under future greenhouse gas (GHG) emissions scenarios. It may well be that the size of the Northern California fires won’t reach the threshold of 50,000 acres used in this study (the top 2% of wildland fires), but if these not-so-large fires are disturbing, then the prospect of even larger ones more frequently in much of the western US is even more so. Continue reading