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Here's an interesting take in a new paper in Science. Oceans more important than CO2?
North Atlantic ocean circulation and abrupt climate change during the last glaciation
Abstract
The last ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3 (MIS3), the glacial interval twenty-five to sixty thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer Pa/Th with the deep water-mass tracer, δ13CBF. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change.
The new study explores what happened to ocean circulation when the Earth went through a series of abrupt climate changes in the past, during a time when ice covered part of North America and temperatures were colder than today. It looks at the Atlantic meridional overturning circulation, which distributes heat as it moves warmer surface water from the tropics toward Greenland and the high northern latitudes and carries colder, deeper water from the North Atlantic southward.
New Paper finds ocean circulation drives the climate on the surface
During the last ice age (and others before it) temperatures across the Northern Hemisphere would abruptly swing up and down by a hefty 3 – 6°C every 1,500 years or so. A new study using isotopes on the sea floor rather provocatively suggests that the Atlantic ocean circulation was to blame. Apparently it slowed almost to halt, and before the surface water cooled. It seems that when the Atlantic currents slow too far they stop bringing warmer water north from the equator and Southern Hemisphere, and thus the north ices over. During these super-cold periods the ice sheets spread down and cover much of North America, (and real estate in Australia costs a motza). Massive icebergs break off and drift, but apparently things took a lot longer to get cold in the Southern Hemisphere, and the north and south possibly got a bit out of whack cooling and warming in opposite phases. The researcher used the word “bipolar”. . . .
Ocean Circulation Implicated in Past Abrupt Climate Changes
June 30, 2016
North Atlantic ocean circulation and abrupt climate change during the last glaciation
[*=left]L. G. Henry1,*,
[*=left]J. F. McManus1,
[*=left]W. B. Curry2,3,
[*=left]N. L. Roberts4,
[*=left]A. M. Piotrowski4,
[*=left]L. D. Keigwin2
- ↵*Corresponding author. Email: lhenry@ldeo.columbia.edu
Abstract
The last ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3 (MIS3), the glacial interval twenty-five to sixty thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer Pa/Th with the deep water-mass tracer, δ13CBF. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change.
The new study explores what happened to ocean circulation when the Earth went through a series of abrupt climate changes in the past, during a time when ice covered part of North America and temperatures were colder than today. It looks at the Atlantic meridional overturning circulation, which distributes heat as it moves warmer surface water from the tropics toward Greenland and the high northern latitudes and carries colder, deeper water from the North Atlantic southward.
New Paper finds ocean circulation drives the climate on the surface
During the last ice age (and others before it) temperatures across the Northern Hemisphere would abruptly swing up and down by a hefty 3 – 6°C every 1,500 years or so. A new study using isotopes on the sea floor rather provocatively suggests that the Atlantic ocean circulation was to blame. Apparently it slowed almost to halt, and before the surface water cooled. It seems that when the Atlantic currents slow too far they stop bringing warmer water north from the equator and Southern Hemisphere, and thus the north ices over. During these super-cold periods the ice sheets spread down and cover much of North America, (and real estate in Australia costs a motza). Massive icebergs break off and drift, but apparently things took a lot longer to get cold in the Southern Hemisphere, and the north and south possibly got a bit out of whack cooling and warming in opposite phases. The researcher used the word “bipolar”. . . .
Ocean Circulation Implicated in Past Abrupt Climate Changes
June 30, 2016