University of Leicester: Antarctica's irregular heartbeat shows signs of rapid melting

[OKIsItJustMe]

https://le.ac.uk/news/2024/december/ice-sheets

Antarctica’s irregular heartbeat shows signs of rapid melting
10 December 2024

Periods of sudden melting in the Antarctic ice sheet have been unearthed in a new climate record from over 20 million years ago by geoscientists led by the University of Leicester and the University of Southampton.

Published in the journal Nature Communications, the new study reveals how sensitive our planet’s early ice ages were to the effect of the Earth’s eccentric orbit around the Sun, suggesting the Antarctic ice sheet is less stable than has been assumed.

It also provides a glimpse of how the Antarctic may behave in a world without the Greenland Ice Sheet, which will melt if emissions continue unabated.

Records show that the Antarctic ice sheet has varied in size throughout its history. These variations in size occur regularly, just like a heartbeat. Existing records from different places in the ocean show different ‘rhythms’ in the heartbeat of early Antarctic ice ages. This should not be possible because the imprint of the waxing and waning of the Antarctic ice sheet on the climate record should be identical everywhere in the ocean, just as it should not be possible that your leg has a different pulse rate than your arm.

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http://dx.doi.org/10.1038/s41467-024-54186-1

[AKwannabe]

1. That is not good

We are effed in so many ways

[OKIsItJustMe]

2. James Hansen et al: ]Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, ...

https://acp.copernicus.org/articles/16/3761/2016/acp-16-3761-2016.pdf

Atmos. Chem. Phys., 16, 3761–3812, 2016
www.atmos-chem-phys.net/16/3761/2016/
doi:10.5194/acp-16-3761-2016
© Author(s) 2016. CC Attribution 3.0 License.

Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous

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Received: 11 June 2015 – Published in Atmos. Chem. Phys. Discuss.: 23 July 2015
Revised: 17 February 2016 – Accepted: 18 February 2016 – Published: 22 March 2016

Abstract. We use numerical climate simulations, paleoclimate data, and modern observations to study the effect of growing ice melt from Antarctica and Greenland. Meltwater tends to stabilize the ocean column, inducing amplifying feedbacks that increase subsurface ocean warming and ice shelf melting. Cold meltwater and induced dynamical effects cause ocean surface cooling in the Southern Ocean and North Atlantic, thus increasing Earth’s energy imbalance and heat flux into most of the global ocean’s surface. Southern Ocean surface cooling, while lower latitudes are warming, increases precipitation on the Southern Ocean, increasing ocean stratification, slowing deepwater formation, and increasing ice sheet mass loss. These feedbacks make ice sheets in contact with the ocean vulnerable to accelerating disintegration. We hypothesize that ice mass loss from the most vulnerable ice, sufficient to raise sea level several meters, is better approximated as exponential than by a more linear response. Doubling times of 10, 20 or 40 years yield multi-meter sea level rise in about 50, 100 or 200 years. Recent ice melt doubling times are near the lower end of the 10–40-year range, but the record is too short to confirm the nature of the response. The feedbacks, including subsurface ocean warming, help explain paleoclimate data and point to a dominant Southern Ocean role in controlling atmospheric CO₂, which in turn exercised tight control on global temperature and sea level. The millennial (500–2000-year) timescale of deep-ocean ventilation affects the timescale for natural CO₂, change and thus the timescale for paleo-global climate, ice sheet, and sea level changes, but this paleo-millennial timescale should not be misinterpreted as the timescale for ice sheet response to a rapid, large, human-made climate forcing. These climate feedbacks aid interpretation of events late in the prior interglacial, when sea level rose to +6–9 m with evidence of extreme storms while Earth was less than 1 ◦C warmer than today. Ice melt cooling of the North Atlantic and Southern oceans increases atmospheric temperature gradients, eddy kinetic energy and baroclinicity, thus driving more powerful storms. The modeling, paleoclimate evidence, and ongoing observations together imply that 2 °C global warming above the preindustrial level could be dangerous. Continued high fossil fuel emissions this century are predicted to yield (1) cooling of the Southern Ocean, especially in the Western Hemisphere; (2) slowing of the Southern Ocean overturning circulation, warming of the ice shelves, and growing ice sheet mass loss; (3) slowdown and eventual shutdown of the Atlantic overturning circulation with cooling of the North Atlantic region; (4) increasingly powerful storms; and (5) non-linearly growing sea level rise, reaching several meters over a timescale of 50–150 years. These predictions, especially the cooling in the Southern Ocean and North Atlantic with markedly reduced warming or even cooling in Europe, differ fundamentally from existing climate change assessments. We discuss observations and modeling studies needed to refute or clarify these assertions.

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