by Nomad
Mon May 25th, 2009 at 03:18:16 AM EST
An interesting article was published in Science last week, concerning the estimated melt from the Antarctic ice sheet, due to the effects of higher temperatures:
From the abstract:
Reassessment of the Potential Sea-Level Rise from a Collapse of the West Antarctic Ice Sheet -- Bamber et al. 324 (5929): 901 -- Science
Theory has suggested that the West Antarctic Ice Sheet may be inherently unstable. Recent observations lend weight to this hypothesis. We reassess the potential contribution to eustatic and regional sea level from a rapid collapse of the ice sheet and find that previous assessments have substantially overestimated its likely primary contribution. We obtain a value for the global, eustatic sea-level rise contribution of about 3.3 meters, with important regional variations.
Emphasis mine; the rest of the article is only available for people with a subscription. But the main point: the estimated 5 - 6 meters of catastrophic sea-level rise has become a little more nuanced.
promoted by whataboutbob
The collapse and melting off the West Antarctic Ice Sheet (WAIS), would result in the largest contribution of global sea-level rise - with dramatic consequences for coastal areas. There have been found indications that the ice sheet has significantly calved back previously in geological times. For instance, it's suspected to have occurred during an interglacial period 400.000 years ago, another period when the earth was not experiencing an ice-age. On a side note, there are indications that this interglacial period is the most similar, in terms of planetary movements, to the interglacial the earth has been experiencing the past 10.000 years. This period could then give the best comparison how today's climate is (or isn't) different.
Previous estimates of the contribution of the WAIS to sea-level rise were calculated using data that since then have been improved:
BBC NEWS | Science & Environment | Ice sheet melt threat reassessed
But Professor Bamber said that no-one had revisited the calculation, despite new data sets becoming available, and scientists developing a better understanding of the dynamics in the vast ice sheets.
The original estimates were based on "very basic ice thickness data", he explained.
"Ice thickness data gives you information about the depth of the bedrock underneath the ice sheet.
"Over the past 30 years, we have acquired much more ice thickness data over the whole of Antarctica, particularly over West Antarctica.
"We also have much better surface topography. Those two data sets are critical in determining two things."
In other words, more precision in determining the volume of the ice sheet, and better detail for determining its integrity. It now seems that the integrity of the WAIS could be more robust than was previously assumed.
The new study brings two important observations:
1) the volume of ice released from a collapse of the WAIS is almost half of what was previously predicted (although still catastrophic in the long run)
2) the period of time in which the collapse will occur could well take longer than was previously estimated (in other words, we don't really know what the rate will be)
The crucial hang-up remains:
BBC NEWS | Science & Environment | Ice sheet melt threat reassessed
Responding to Professor Bamber's paper in Science, British Antarctic Survey science leader Dr David Vaughan described the findings as "quite sound".
"But for me, the most crucial question is not solely about the total amount of ice in West Antarctica, because that might take several centuries to be lost to the ocean," he told BBC News.
"The crucial question is how much ice could be lost in 100-200 years; that's the sea level rise we have to understand and plan for.
While I'm at it, there may have been a few more messages that might not have reached a large audience. For instance:
I list those things on purpose, because I suspect that for many these events do not easily fit in the concept of an increasingly warmer climate. What they are, is this: little wiggles and minor variations on the bigger climate curve. Do they matter; who can say? (I sure won't try.)
But the point is that these messages are not in line with the expectations of many who've been mostly hearing about those articles that predict imminent (or even not-so imminent) catastrophes. What's more, I won't be surprised either that at some point they will be seized by people who prefer to maintain business-as-usual. When people use climate change on Mars as an argument, or a few cold winters, then certainly these will suffice...
