"A persistent chill in the ocean off Antarctica that defies the global warming blamed for melting Arctic ice at the other end of the planet is caused by cold waters welling up from the depths after hundreds of years, scientists said on Monday.
The Southern Ocean off Antarctica may be among the last places on Earth to feel the impact of man-made climate change, with a lag of centuries to affect waters emerging from up to 5,000 meters (16,000 ft) deep, the U.S. study said.
Many
people who doubt mainstream scientific findings that human use of
fossil fuels is warming the planet often point to the paradox of
expanding winter sea ice off Antarctica in recent decades....
"Our
findings are a step toward resolving the mystery," lead author Kyle
Armour of the University of Washington, Seattle, told Reuters of the
study in the journal Nature Geoscience.
He
noted the upwelling of cold water helped to explain the persistence of
sea ice but not its expansion, a trend other studies have linked to
shifts in winds off the vast frozen continent.
Monday's
report found that warm waters in the Gulf Stream cool as they flow
north into the North Atlantic, then sink and loop south towards
Antarctica as part of an aquatic conveyor belt that takes centuries to
complete.
Eventually,
gale force winds in the Southern Ocean around Antarctica blow surface
waters northwards and draw the chill, ancient waters from the depths.
That
upwelling helps explain why the surface of the Southern Ocean have
warmed by just 0.02 degree Celsius (0.036 Fahrenheit) per decade since
1950, a fraction of the global average of 0.08 degree (0.144F), the
study said.
It
was unclear if the cold waters could delay a melt of ice locked up on
land in Antarctica, the biggest worry about the continent that could
sharply raise global sea levels."...
===============
May 30, 2016, "Southern Ocean warming delayed by circumpolar upwelling and equatorward transport," Nature Geoscience, Armour et al.
===============
May 30, 2016, "Southern Ocean warming delayed by circumpolar upwelling and equatorward transport," Nature Geoscience, Armour et al.
===============
Added: Arctic Sea Ice Area doing well too, per University of Illinois at Urbana-Champaign, Polar Research Group, May 29, 2016, 3 charts
Above, May 29, 2016, "Northern Hemisphere Sea Ice Area," The Cryosphere Today, University of Illinois at Urbana-Champaign, Polar Research Group
Above, May 29, 2016, "Northern Hemisphere Sea Ice Anomaly," uiuc.edu
Above, May 29, 2016, "Northern Hemisphere Sea Ice Area," uiuc.edu, "data provided by NSIDC: NASA SMMR and SSMI,"University of Illinois at Urbana-Champaign, Polar Research Group
Above, May 29, 2016, "Northern Hemisphere Sea Ice Area," The Cryosphere Today, University of Illinois at Urbana-Champaign, Polar Research Group
Above, May 29, 2016, "Northern Hemisphere Sea Ice Anomaly," uiuc.edu
Above, May 29, 2016, "Northern Hemisphere Sea Ice Area," uiuc.edu, "data provided by NSIDC: NASA SMMR and SSMI,"University of Illinois at Urbana-Champaign, Polar Research Group
===============
Added: "Climate change not so global," Northern and Southern hemispheres are different, per 2014 peer reviewed study. Arctic and Antarctic can't be compared. No "global one-size-fits-all:”
“This study reverses previous findings."
8/4/2014, "Climate change not so global," University of Queensland, Australia
"Scientists are calling for a better understanding of regional climates, after research into New Zealand's glaciers has revealed climate change in the Northern Hemisphere does not directly affect the climate in the Southern Hemisphere.
The University of Queensland study showed that future climate changes may impact differently in the two hemispheres, meaning a generalised global approach isn’t the solution to climate issues.
UQ School of Geography, Planning and Environmental Management Head Professor Jamie Shulmeister said the study provided evidence for the late survival of significant glaciers in the mountains of New Zealand at the end of the last ice age – a time when other ice areas were retreating.
“This study reverses previous findings which suggested that New Zealand's glaciers disappeared at the same time as ice in the Northern Hemisphere,” he said.
“We showed that when the Northern Hemisphere started to warm at the end of the last ice age, New Zealand glaciers were unaffected.
“These glaciers began to retreat several thousand years later, when changes in the Southern Ocean led to increased carbon dioxide emissions and warming.
”This indicates that future climate change may impact differently in the two hemispheres and that changes in the Southern Ocean are likely to be critical for Australia and New Zealand.”
The study used exposure dating of moraines - mounds of rocks formed by glaciers - to reconstruct the rate of ice retreat in New Zealand’s Ashburton Valley after the last glacial maximum – the time when the ice sheets were at their largest.
The researchers found that the period from the last glacial maximum to the end of the ice age was longer in New Zealand than in the Northern Hemisphere.
They also found that the maximum glacier extent in New Zealand occurred several thousand years before the maximum in the Northern Hemisphere, demonstrating that growth of the northern ice sheets did not cause expansion of New Zealand glaciers.
“New Zealand glaciers responded largely to local changes in the Southern Ocean, rather than changes in the Northern Hemisphere as was previously believed,” Professor Shulmeister said.
“This study highlights the need to understand regional climate rather than a global one-size-fits-all.”
The research was conducted in collaboration with the University of Griefswald, Germany, the Australian Nuclear Science and Technology Organisation, and the University of Canterbury, New Zealand, and published in the Proceedings of the National Academy of Science in July."
=============================
2014 PNAS study cited in above Queensland article:
7/28/2014, "The early rise and late demise of New Zealand’s last glacial maximum," PNAS.org, Henrik Rothera,1 David Finkb, James Shulmeisterc, Charles Mifsudb, Michael Evansd, and Jeremy Pughe,2
.
"Significance"...
"This record from a key site in the midlatitude Southern Hemisphere shows that the largest glacial advance did not coincide with the coldest temperatures during this phase. We also show that the regional post-LGM ice retreat was very gradual, contrary to the rapid ice collapse widely inferred. This demonstrates that glacial records from New Zealand are neither synchronous with nor simply lag or lead Northern Hemisphere ice sheet records, which has important implications for the reconstruction of past interhemispheric climate linkages and mechanisms.".
"Abstract"
"Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the last glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models....These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early last glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka."
"This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1401547111/-/DCSupplemental."
=====================
“This study reverses previous findings."
8/4/2014, "Climate change not so global," University of Queensland, Australia
"Scientists are calling for a better understanding of regional climates, after research into New Zealand's glaciers has revealed climate change in the Northern Hemisphere does not directly affect the climate in the Southern Hemisphere.
The University of Queensland study showed that future climate changes may impact differently in the two hemispheres, meaning a generalised global approach isn’t the solution to climate issues.
UQ School of Geography, Planning and Environmental Management Head Professor Jamie Shulmeister said the study provided evidence for the late survival of significant glaciers in the mountains of New Zealand at the end of the last ice age – a time when other ice areas were retreating.
“This study reverses previous findings which suggested that New Zealand's glaciers disappeared at the same time as ice in the Northern Hemisphere,” he said.
“We showed that when the Northern Hemisphere started to warm at the end of the last ice age, New Zealand glaciers were unaffected.
“These glaciers began to retreat several thousand years later, when changes in the Southern Ocean led to increased carbon dioxide emissions and warming.
”This indicates that future climate change may impact differently in the two hemispheres and that changes in the Southern Ocean are likely to be critical for Australia and New Zealand.”
The study used exposure dating of moraines - mounds of rocks formed by glaciers - to reconstruct the rate of ice retreat in New Zealand’s Ashburton Valley after the last glacial maximum – the time when the ice sheets were at their largest.
The researchers found that the period from the last glacial maximum to the end of the ice age was longer in New Zealand than in the Northern Hemisphere.
They also found that the maximum glacier extent in New Zealand occurred several thousand years before the maximum in the Northern Hemisphere, demonstrating that growth of the northern ice sheets did not cause expansion of New Zealand glaciers.
“New Zealand glaciers responded largely to local changes in the Southern Ocean, rather than changes in the Northern Hemisphere as was previously believed,” Professor Shulmeister said.
“This study highlights the need to understand regional climate rather than a global one-size-fits-all.”
The research was conducted in collaboration with the University of Griefswald, Germany, the Australian Nuclear Science and Technology Organisation, and the University of Canterbury, New Zealand, and published in the Proceedings of the National Academy of Science in July."
=============================
2014 PNAS study cited in above Queensland article:
7/28/2014, "The early rise and late demise of New Zealand’s last glacial maximum," PNAS.org, Henrik Rothera,1 David Finkb, James Shulmeisterc, Charles Mifsudb, Michael Evansd, and Jeremy Pughe,2
.
"Significance"...
"This record from a key site in the midlatitude Southern Hemisphere shows that the largest glacial advance did not coincide with the coldest temperatures during this phase. We also show that the regional post-LGM ice retreat was very gradual, contrary to the rapid ice collapse widely inferred. This demonstrates that glacial records from New Zealand are neither synchronous with nor simply lag or lead Northern Hemisphere ice sheet records, which has important implications for the reconstruction of past interhemispheric climate linkages and mechanisms.".
"Abstract"
"Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the last glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models....These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early last glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka."
"This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1401547111/-/DCSupplemental."
=====================
.................
No comments:
Post a Comment