The West Antarctic Ice Sheet Is Doomed — but don’t sell the beach house!

Three recent studies on the West Antarctic Ice Sheet (WAIS) are making waves in the media, re-stoking fears of catastrophic sea-level rise, and putting a spring in the step of many a carbon-taxer.

Thomas Sumner summarizes two of the studies in a Science magazine commentary titled “No Stopping the Collapse of the West Antarctic Ice Sheet.” The studies, he writes, conclude that:

Thwaites Glacier, a keystone holding the massive West Antarctic Ice Sheet together, is starting to collapse. In the long run, they say, the entire ice sheet is doomed. Its meltwater would raise sea levels by more than 3 meters.

Specifically, Joughin et al., writing in Science, find that “in as few as 2 centuries Thwaites Glacier’s edge will recede past an underwater ridge now stalling its retreat. Their models suggest that the glacier will then cascade into rapid collapse.” Rignot et al., writing in Geophysical Research Letters (GRL), “describes recent radar mapping of West Antarctica’s glaciers and confirms that the 600-meter-deep ridge is the final obstacle before the bedrock underlying the glacier dips into a deep basin.”

In addition, McMillan et al., also writing in GRL, report that Antarctica as a whole is losing about 159 billion tons of ice per year. That’s an amount larger than previous estimates and translates to an overall sea-level rise contribution of 0.45 mm/year (1.7 inches per century).

The first two studies expressly conclude that the Thwaites and neighboring outlet glaciers have retreated to a point of no return and that, once gone, nothing can prevent the rest of the WAIS from flowing into the sea.

My initial reaction was: What’s really new here?

Conway et al. (1999), a study of the relentless retreat of WAIS grounding line since the early Holocene (i.e. 9,000 years ago or more), and Bindschadler (2006), a study of the inexorable melting of submarine glaciers in contact with warm ocean currents, both concluded that the WAIS is doomed.

We can also infer as much from Dahl-Jensen et al. (2013), who found that in the last interglacial period, Greenland retained about 75% of its mass despite enduring temperatures 4°C-8°C warmer than the present for 6,000 years. Sea levels were 4-8 meters higher at the end of the last interglacial than at present, so much of that extra water must have come from Antarctica.

Thus, it is reasonable to assume that, anthropogenic global warming or no, the WAIS will someday be gone and sea levels will be several meters higher.

What’s new in the recent studies, apparently, is improved accuracy in estimating ice mass loss rates, and a shorter timetable than previously estimated for the demise of the WAIS. Joughin et al. expect the onset of rapid collapse to begin in 2 to 9 centuries.

There is no new insight for policy, though. If WAIS disintegration is unstoppable, regulating or taxing carbon is not going to save it. As Cato Institute Chip Knappenberger points out, using EPA climate sensitivity assumptions, even if the U.S. shut down its entire economy tomorrow, that would avert less than 0.2°C of warming by 2100.  That’s not enough to detectably slow WAIS ice loss rates much less stop the unstoppable.

Joughin et al. estimate that sea-level rise from Thwaites glacier retreat and thinning will be “moderate” over the course of the 21^st century – less than 0.25 mm/year. That translates to 0.9 inches of additional sea-level rise. To be sure, the current rate of ice loss from Antarctica could increase during the decades to come. But at present, according to McMillan et al., all of Antarctica is contributing 1.7 inches per century to global sea level rise. That’s not a good reason to sell the beach house! For perspective, sea levels have risen about 8 inches since 1880.

The “crisis” spin on these studies is a trick of the imagination. People tend to imagine cities as immovable entities, stuck in harm’s way. But cities move continually in terms of where people build and live. If sea-level rise from Antarctica noticeably accelerates (whether in coming decades or after 2100), urban planners and real estate markets will alter development patterns accordingly.

The appropriate policy response remains adaptation. Indeed, as my colleague William Yeatman reminds us, although much of Holland is at and below sea level, the Dutch built a flourishing society in the 16^th and 17^th centuries with pre-modern technology. How much better will sea defenses be in century of Captain James Tiberius Kirk, or those of his great, great, great grandchildren?