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What's Up In Climate Change? Gulf stream weakens, Antarctic melt speeds up and tracking climate commitments for Paris 2015

Scott Sutherland
Meteorologist/Science Writer

Friday, March 27, 2015, 7:17 PM - Greenland melting could be pushing the Gulf Stream towards a breakdown, Antarctic ice shelves are thinning rapidly, and new maps let you track the progress of the world's nations towards the UN Climate Conference in Paris later this year. It's what's up in climate change.

Gulf Stream Weakens Due to Greenland Melting?

If you happened to read about this past winter topping charts as the warmest December-February period on record so far, around the globe, you may recognize the graphic below. However, one detail of it is now being highlighted, namely a conspicuous cold spot.

Credit: NOAA. Edited by Scott Sutherland

The only place on the planet that had 'record coldest' temperatures during this past northern winter was the North Atlantic Ocean. Normally, this region is fairly warm, even during the winter, as the Gulf Stream - the warm current of water up the east coast of North America - flows right through there on its way towards northern Europe. However, the above map shows the most recent results from a significant cooling trend that scientists have been noticing for some time.

According to Stefan Rahmstorf, of Potsdam University in Germany:

It happens to be just that area for which climate models predict a cooling when the Gulf Stream System weakens (experts speak of the Atlantic meridional overturning circulation or AMOC, as part of the global thermohaline circulation). That this might happen as a result of global warming is discussed in the scientific community since the 1980s – since Wally Broecker’s classical Nature article "Unpleasant surprises in the greenhouse?" Meanwhile evidence is mounting that the long-feared circulation decline is already well underway.

In a study published this week, Rahmstorf, along with colleagues that included Michael Mann (Penn State climate scientist) and Jason Box (who runs the Dark Snow Project), showed evidence that this cold spot, and the weakening of the Gulf Stream that it represents, may be due to the melting of Greenland's glaciers. As is seen in the waters around Antarctica, fresh water pouring into the oceans from melting glaciers doesn't mix well with the salt water. Due to differences in density, the fresh water forms a layer on the surface. This is likely at least partly responsible for the increase in sea ice around Antarctica in recent years, but in the North Atlantic, this effect has a direct impact on the warm surface currents of the Gulf Stream.

WATCH BELOW: 'The Day After Tomorrow' may have been riddled with inaccuracies, but as Rahmstorf, Mann and Box discuss, there are parts of it that ring true, even in the real world.

The research paper, which was published in Nature Climate Change, discusses a partial recovery of the slowdown that's been evident since the 1970s. 

However, as Rahmstorf told the Washington Post: "These new NOAA data got me quite worried because they indicate that this partial recovery that we describe in the paper was only temporary, and the circulation is on the way down again."

Mann added to this by illustrating what really could happen along the east coast of North America if the Gulf Stream slows down, detailing how warmer waters to the east of the Gulf Stream and cooler waters to the west of it form a slope - higher in the east due to thermal expansion of the water. This makes the waters off the US Northeast and Atlantic Canada naturally lower than in other regions of the Atlantic.

"So if you weaken the Gulf Stream and weaken that temperature contrast … sea level off the U.S. east coast will actually rise!" Mann told the Washington Post in an email.

Antarctic Ice Shelves Thinning

As shown in the video above, nearly two decades of overlapping satellite data from different missions is showing how Antarctica's glaciers are responding to climate change.

According to the Scripps Institution of Oceanography:

Total ice shelf volume (mean thickness multiplied by ice shelf area) across Antarctica changed very little from 1994 to 2003, then declined rapidly, the study shows. West Antarctic ice shelves lost ice throughout the entire observation period, with accelerated loss in the most recent decade. Earlier gains in East Antarctic ice shelf volume ceased after about 2003, the study showed.  Some ice shelves lost up to 18 percent of their volume from 1994 to 2012.
"Eighteen percent over the course of 18 years is really a substantial change," said [Scripps graduate student Fernando Paolo]. "Overall, we show not only the total ice shelf volume is decreasing, but we see an acceleration in the last decade."
While melting ice shelves do not contribute directly to sea-level rise, the researchers indicate that there is an important indirect effect.
"The ice shelves buttress the flow from grounded ice into the ocean, and that flow impacts sea-level rise, so that’s a key concern from our new study," said [
Scripps glaciologist Helen Amanda Fricker].

While the study looked at the rates of change, it did not investigate the specific reasons behind them. These will be investigated in future studies. However, this study showed that, at the rate these West Antarctica ice shelves are currently thinning, they could lose half their ice volume within the next 2 centuries.

Tracking Climate Commitments for Paris 2015

Interested in watching the progress (or lack thereof) leading up to the UN Climate Conference in Paris? A new interactive map from the World Resources Institute is tracking who has submitted their Intended Nationally Determined Contribution (INDC), and what, exactly, those INDCs include.

The European Union (including French Guiana in South America) is the only one on the map so far. That's not very encouraging, given that we're now 4 days away from the submission deadline, but the map may begin to fill up at the last minute (at least we can hope!). Let's not minimize what we're trying to do here, though. These shouldn't be idle commitments, easily set aside. Some countries may end up being late, but if we can produce real commitments that bring about real results, it will (again, hopefully) be worth it.

Click on the "View Pre-2020s Map" and things are a bit better, however those are old commitments, made in 2009 and 2010, and may not be up to the task now.

Sources: Real Climate | Washington PostScripps Institution of Oceanography | Real Climate | World Resources Institute

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