Saddle collapse behind rapid sea level rise

September 20, 2012
Saddle collapse behind rapid sea level rise
Credit: Shutterstock

Researchers from the University of Bristol in the United Kingdom have uncovered the mystery behind the rapid sea level rise in the past by using climate and ice sheet models. Funded in part by a Marie Curie Action grant under the EU's Seventh Framework Programme (FP7), the results showed that the process, called 'saddle collapse', generated two rapid sea level rise events: the Meltwater pulse 1a (MWP1a), some 14,600 years ago, and the '8,200 year' events. The results were published in the journal Nature.

While researchers have tried to discover what triggered these events, no concrete information was ever found, until now. Dr Lauren Gregoire from the School of Geographical Sciences at the University of Bristol and colleagues observed how the events triggered the collapse and separation of ice domes over North America, thus resulting in rapid melting and the opening of an ice-free corridor.

Ice domes that were up to three kilometres thick were formed in areas of high and higher like the . The ice sheet consisted of the saddles, which were lower valleys of ice between the domes.

Researchers say the climate warmed naturally towards the end of the . In this study, the scientists found that the ice melted at increasingly high elevations, and later reached and melted the saddle area between the ice domes. They observed that the melting saddle shrank, reaching warmer altitudes and melting more quickly. The end result was a completely melted saddle. Within 500 years, the saddles were gone and only the ice domes remained.

The researchers said the melted ice flowed into the oceans, generating rapid sea level rises of 9 metres in 500 years during the Meltwater pulse 1a event 14,600 years ago and 2.5 metres in the second event, 8,200 years ago.

'We didn't expect our model to produce such a rapid ,' said lead author Dr Gregoire. 'We got really excited when we realised that the events we simulated corresponded to real events! The pulse produced by the saddle-collapse can explain more than half of the sea level jump observed around 14,600 years ago. The rest probably came from the progressive melting of ice sheets in Europe and Antarctica.'

According to the researchers, the results identify the process that triggered the melting of the North American ice sheet and resulted in the rapid sea level rises in the past. However, they also provide insight into the nature of ice sheets and climate change.

They add that this study can lead to more testing of climate and ice sheet models. These types of models could reflect patterns observed in natural records, and in turn increase people's confidence in them.

Explore further: Geoscientists discover trigger for past rapid sea level rise

More information: Gregoire, L.J., et al. 'Deglacial rapid sea level rises caused by ice-sheet saddle collapses', Nature, 2012, 487. doi:10.1038/nature11257

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2.2 / 5 (13) Sep 20, 2012
Record sea ice growth in Antarctica.

3.5 / 5 (11) Sep 20, 2012
Yes, the record growth of sea ice in Antarctica this winter is in part caused by the continental ice flowing toward the sea. As the melt rate increases the flow rate does as well.

A nice chart showing the decline in global sea ice area can be found here.


Currently global sea ice area is around 1.8 million kilometers below historical norms.
3.6 / 5 (14) Sep 20, 2012
The article in Forbes by the way is written by the Heritage Foundation - one of the most corrupt propaganda groups in America.

Heritage is disparately trying to change the subject from the ongoing collapse of the northern ice cap to anything else.

Only the most foolish of fools are listening.
2.5 / 5 (6) Sep 20, 2012
@VendicarD Are there charts that go back hundreds of years, or has it been impossible to measure sea ice until recently? Also, on what is the 'norm' based? Thanks.
4.1 / 5 (9) Sep 20, 2012
@VendicarD Are there charts that go back hundreds of years, or has it been impossible to measure sea ice until recently? Also, on what is the 'norm' based? Thanks.

There aren't charts that go back hundreds of years, however you can search arctic ice extent and find some reasonably accurate estimations based on sediment cores and ice core data. The 'norm' is the 1979-2000 median extent, since satelite monitoring began.
4.2 / 5 (5) Sep 20, 2012
@VendicarD Are there charts that go back hundreds of years, or has it been impossible to measure sea ice until recently? Also, on what is the 'norm' based? Thanks.

Sorry, bertibus, but even the most unshcooled commentors here know the answer to that question, and are aware of the well validated proxy data available which are used to create the record prior to the advent of instrument-generated data.

Since you are an occasional poster here, one can be forgiven the presumption that your comment was meant in a merely provocative sense, and not as a sincere plea for information of which you weren't already in possession.

Your comment doesn't even rate as a "nice try".

4.4 / 5 (7) Sep 20, 2012
Record sea ice growth in Antarctica.
Compare the palpable Arctic decline:

With the almost-nonexistent Antarctic "growth":

Moreover, this is just surface area. The real problem is ice volume:


This shows a much steadier trend than just surface area.

Lastly, the reduction in Arctic ice cover **AND** increase in Antarctic sea ice are BOTH predicted by global climate models. Reason is, Arctic ocean is being melted by warm waters flowing north, while Antarctica's landmass is experiencing increased snowfall due to higher atmospheric humidity. Antarctic sea ice is expected to begin shrinking by mid-century, because global warming will begin causing more precipitation in the form of rain rather than snow.
3.7 / 5 (3) Sep 21, 2012
Record sea ice growth in Antarctica.

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