Over the course of continuous satellite monitoring, the sea-ice has expanded over the course of time, which seems to be contrary to global warming caused by increasing concentrations of greenhouse gasses. A multi-decadal swing of the tropical is shown in a study by an international team of scientists.
Sea ice, which covers a large portion of the ocean surface in the polar regions, plays an important role in controlling global temperatures. Sea-ice coverage is expected to amplify greenhouse gas-caused global warming. Changes in sea ice affect energy exchanges between the ocean and atmosphere, carbon capture by the ocean, and the thermohaline oceanic circulation.
Monitoring long-term changes in global sea ice and ensuring that physical processes that lead to those changes are accurately depicted in climate prediction models is of paramount importance.
There is a difference between simulations and observations.
The global warming trend is consistent with the marked decreases in sea ice over the satellite era. Small but increasing trends have been observed in the Southern Hemisphere. Climate models are able to reproduce the observed decreases in the sea-ice in the northern part of the planet, but they are not able to capture the expansion of the sea-ice in the southern part.
Climate scientists have been perplexed by the observed sea-ice expansion and model-observation discrepancy for more than a decade.
The issue of the observed sea-ice expansion has remained as one of the various hypotheses proposed to explain it.
Increased concentrations of greenhouse gasses and/or stratospheric ozone depletion are linked to natural variability of the climate system, which occurs without direct connections with human activities.
To determine the main causes of the observed sea-ice expansion and model-observation discrepancy, the scientists turned their attention to a longer record of Southern Ocean sea surface temperatures.
Natural variability and regional model biases are to blame for mismatch.
Over a certain period of time, Southern Ocean cooling and associated atmospheric and oceanic circulation changes linked to natural variability in the tropics may temporarily outweigh the opposing human-caused changes, thus resulting in temporary sea ice expansion. It doesn't explain the model-observation discrepancy.
The Southern Ocean multi-decadal variability is closely linked to tropical natural variability in climate according to the co-author and assistant professor of oceanography from the UH Mānoa School of Ocean and Earth Science and Technology. In model simulations, human-caused ocean surface warming dominates.
More information: Eui-Seok Chung et al, Antarctic sea-ice expansion and Southern Ocean cooling linked to tropical variability, Nature Climate Change (2022). DOI: 10.1038/s41558-022-01339-z Journal information: Nature Climate Change Citation: Antarctic sea-ice expansion in a warming climate (2022, April 22) retrieved 22 April 2022 from https://phys.org/news/2022-04-antarctic-sea-ice-expansion-climate.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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