Tag: Younger Dryas

Greenland melt record likely

Jason Box reports that the Greenland ice sheet darkening recorded in satellite albedo ((High albedo = very white, lots of reflection; low albedo = darker, more heat absorbed)) measurements is setting new records this summer, especially at high altitudes. Box recently blogged that ice sheet reflectivity this summer “has been the lowest since accurate records began in March, 2000”.

Here’s the latest “noodle plot” ((Looks like a spaghetti graph to me. What is it with climate people and pasta?)) (regularly updated here) for the ice sheet between elevations of 2,000 and 2,500 metres. 2012 (the black line) is well down into new record territory:

2000 2500 Greenland Ice Sheet Reflectivity Byrd Polar Research Center

Box comments:

What I expect we will see if these low albedo conditions persist is 100% surface melting over the ice sheet. This would be a first in observations. It may not happen this year, but the trajectory the ice sheet is on, along with amplified Arctic warming, will have the ice sheet responding by melting more and more.

To see this darkening in action, have a look at the MODIS image of the west Greenland ice sheet here. You can see the surface melt spreading inland and upwards, grey ice dotted with blue lakes. Add another interesting, if depressing, graph to the panoply of information on the Arctic summer. The sea ice doesn’t look too good either…

In other Greenland-related news, a new study published in Proceedings of the National Academy of Science by Liu et al ((Zhengyu Liu, Anders E. Carlson, Feng He, Esther C. Brady, Bette L. Otto-Bliesner, Bruce P. Briegleb, Mark Wehrenberg, Peter U. Clark, Shu Wu, Jun Cheng, Jiaxu Zhang, David Noone, and Jiang Zhu. Younger Dryas cooling and the Greenland climate response to CO2. Proceedings of the National Academy of Sciences, June 25, 2012 DOI: 10.1073/pnas.1202183109 – PDF here.)), Younger Dryas cooling and the Greenland climate response to CO2 (Science Daily, PNAS abstract), looks at the ice sheet temperature record inferred from the oxygen isotope measurements taken from ice cores, and concludes that they may overestimate the extent of the Younger Dryas cooling. This is interesting stuff for those who have been following the Easterbrook story, because Don places great store by the ice core temperature record. He was wrong before this paper hit the presses, but he’s even wronger now!

Core blimey, Easterbrook’s at it again

Don Easterbrook’s strange obsession with the Greenland temperature record and the GISP2 ice core data series continues. Despite his last effort having been shown to be completely clueless (though still good enough for Bob Carter and “potty peer” Chris Monckton to reference approvingly), he continues to (snow)plough a lonely furrow. This time it’s in a guest post at µWatts headlined (rather poorly) Easterbrook on the magnitude of Greenland GISP2 ice core data. It’s BIG data, obviously, for Don, but sadly he shows no signs of actually doing any proper research, or developing any real understanding of the issues he feels so free to write about.

So where are the errors this time?

Continue reading “Core blimey, Easterbrook’s at it again”

Take a peek at Pukaki’s climate history

Irishmantreambasin.jpg

High in the Ben Ohau range to the west of Lake Pukaki in the South Island’s Mackenzie basin, the glacial moraines in the Irishman Stream Basin (Google Map) are providing important confirmation that the southern hemisphere warmed during a rapid northern hemisphere cooling event at the end of the last ice age. In a new paper in Nature, Glacier retreat in New Zealand during the Younger Dryas stadial Michael Kaplan and a team including three NZ scientists reconstruct the retreat of the glacier that used to fill the basin.

The team dated the sequence of moraines (piles of rock left by the retreating glacier) by measuring the “cosmogenic” beryllium isotope (10Be) in quartz crystals in the rocks — formed by bombardment by cosmic rays — giving a measure of how long the rocks have been exposed to the sky. By modelling the amount of ice in the valley at various moraine positions, they were able to reconstruct the glacier’s decline as the local climate warmed.

Why is this important? Because it’s another important bit of evidence in piecing together the sequence of events as the world warmed up from the last ice age — and in particular because the precise dating confirms that the Younger Dryas cold spell was not global in effect. From the abstract:

Our late-glacial glacier chronology matches climatic trends in Antarctica, Southern Ocean behaviour and variations in atmospheric CO2. The evidence points to a distinct warming of the southern mid-latitude atmosphere during the Younger Dryas and a close coupling between New Zealand’s cryosphere and southern high-latitude climate. These findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the North Atlantic led to a strong interhemispheric thermal gradient during late-glacial times, in turn leading to increased upwelling and CO2 release from the Southern Ocean, thereby triggering Southern Hemisphere warming during the northern Younger Dryas.

See also Science Daily. Ref: Kaplan et al. Glacier retreat in New Zealand during the Younger Dryas stadial. Nature (2010) vol. 467 (7312) pp. 194-197

[Edited to correct my original abysmal geography fail – wrong lake in the title]

Wake of the flood

About 15,000 years ago the world began to warm out of the last ice age. The huge ice sheets that covered North America and Northwest Europe began to melt, and sea level began to rise. But 12,900 years before present, the climate of much of the northern hemisphere made a rapid return to full ice age conditions — cooling by as much as 10ºC. The Big Freeze, as it’s sometimes called, could have started in as little as one season. The cold snap lasted 1,300 years before warming resumed and the current interglacial began. This cooling episode is known as the Younger Dryas, because it was associated with an increase in pollen of the Arctic plant Dryas octopetala in Norwegian lake sediments.

Continue reading “Wake of the flood”