Sea Ice Extent (Global Antarctic and Arctic) – Day 166 – 2019

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5 Million years of cooling

Reblogged from Clive Best:

Why did the earth cool ~6C during the Pleistocene resulting in the current deep ~100 Ky glacial cycles? The most probable cause  is plate tectonics – the opening of the Atlantic and continuing rise of the Himalayas after India collided with Asia. Less well known though is the increasing height of the Andes, Greenland and Western US as shown below. All  data are from the PaleoDEM project

an alternative view of this is though contour plots

We can quantify the net change in land topography by calculating the surface area of the earth above a certain height. This shows that over the last 5 million years there has been an increase in land surfaces above 3000m altitude by 5.4 million square km. That figure represents a net global increase of 56% in such high altitude land masses. This land movement is concentrated in the Himalayas, the western coasts of America and Greenland. These last two extend into high latitudes where changes in albedo are important. So how might this affect this global climate?

1. High altitudes are colder simply due to the fall in temperature with lapse rate. Above 3000m is something like 20C colder than at sea level.  Moisture falls as snow and glaciers develop.

2. A 50% increase in glaciated areas increases global albedo thereby reducing net incoming solar radiation slightly, which I estimate at about 0.5% or up to 2W/M2.  Perhaps just as important a result is that Milankovitch orbital forcing gets amplified as more land remains permanently glaciated at higher latitudes. This amplification effect is evident in the Ice Volume data.

 

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When did Antarctica become permanently ice covered? Prior to 2.5My ago the “West Antarctic Ice Sheet and Antarctic Peninsula Ice Sheets together grew successively larger, with periodic collapses during interglacials. During periods of West Antarctic Ice Sheet absence, the Antarctic Peninsula Ice Sheet remained as a series of island ice caps” (source). This might also explain why initially glacial cycles followed the obliquity cycle since NH insolation and SH insolation are out of phase. Changes in Ice volume partially cancel if Antarctica also contributes to sea levels due to land based melt-back. In this case the MPT (Mid Pleistocene Transition) may represent the end of this cancelation effect  and the start  of NH dominance.

Emperor Penguins “Wiped Out”

NOT A LOT OF PEOPLE KNOW THAT

By Paul Homewood

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Thousands of emperor penguin chicks drowned when the sea-ice on which they were being raised was destroyed in severe weather.

The catastrophe occurred in 2016 in Antarctica’s Weddell Sea.

Scientists say the colony at the edge of the Brunt Ice Shelf has collapsed with adult birds showing no sign of trying to re-establish the population.

And it would probably be pointless for them to try as a giant iceberg is about to disrupt the site.

The dramatic loss of the young emperor birds is reported by a team from the British Antarctic Survey (BAS).

Drs Peter Fretwell and Phil Trathan noticed the disappearance of the so-called Halley Bay colony in satellite pictures.

It is possible even from 800km up to spot the animals’ excrement, or guano, on the white ice and then to estimate the likely size of any gathering.

But the Brunt population, which had sustained…

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Antarctic: ‘No role’ for climate in Halley iceberg splitting

NOT A LOT OF PEOPLE KNOW THAT

By Paul Homewood

h/t Philip Bratby

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When a giant iceberg breaks away from near Britain’s Halley research base, it won’t be because of climate change.

Scientists Jan De Rydt and Hilmar Gudmundsson have spent years studying the area and say the calving will be the result of natural processes only.

The Antarctic station, which sits on a floating platform of ice, was moved in 2017 to get it away from a large chasm.

That crack is now expected to dump a berg the size of Greater London into the Weddell Sea.

It’s not clear precisely when this will happen, but the breakaway looks imminent, prompting the British Antarctic Survey (BAS) to withdraw its staff from Halley as a precaution.

As soon as the calving does occur, though, it can be guaranteed that one of the first questions everyone will ask is: what was the influence of climate change?

And the…

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Large Antarctic Ice Shelf Is About To Break Apart And There Is One Shocking Thing

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The shocking thing is …. they tell people it is natural!

Now academics from Northumbria University, in Newcastle upon Tyne, UK, in collaboration with scientists from ENVEO, a remote sensing company in Austria, have submitted new research to the journal The Cryosphere, which shows that the break-off is part of the ice shelf’s natural lifecycle, and that similar events may have occurred in the past.

As Professor Hilmar Gudmundsson of Northumbria explains: “I have been carrying out research in this area for more than 15 years and have been monitoring the growth of the cracks since they first emerged in 2012.

“Satellite images of the changes in the ice shelf have been shared online and there has been much speculation about the cause of this movement and the impact the iceberg will have when it breaks away.

“However, what many people do not realise is that this is…

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