Melting ice caps may not shut down ocean current

A new research led by scientists at the University of Wisconsin suggests that most simulations of our climate's future may be too sensitive to the melting of the ice in the north.

Climate scientists count the AMOC as one of the biggest tipping points on the way to a planetary climate disaster. The Atlantic Ocean current carries warm tropical surface water north and cooler deeper water south.

We have been taught to picture it like a conveyor belt, even in middle school and high school, that shuts down when freshwater comes in from ice melt.

He says researchers are revising their understanding of the relationship between AMOC and freshwater from melting polar ice.

A 14,500-year-old, sharp global temperature hike and a stalled AMOC have accompanied abrupt climate events in the past. He conducted a climate model while a graduate student at the University of Wisconsin-Madison.

He says that reproducing the abrupt warming about 14,700 years ago that is seen in the paleoclimate record was a success.

The 2009 model couldn't keep up with Earth's temperatures, which cooled after this abrupt warming before rising again to new highs for the last 10,000 years. The increase in temperatures seen in geological archives of climate, like ice cores, did not match the warming seen in the simulations.

A new model simulation that matches the warmth of the last 10,000 years was described by He and Peter Clark in a study published this week in the journal Nature Climate Change. Most scientists believe that the AMOC stalls or is shut down because of the Trigger.

Warming temperatures on Earth cause sea ice to melt, releasing fresh water into the ocean. The density differences in the North Atlantic that make the AMOC's north-bound water sink and turn back south were believed to be disrupted by the freshwater influx.

He says the problem is with the geological climate data.

The AMOC barely changed despite the climate record showing an abundance of freshwater that came from the final melting of the ice sheets over North America and Europe. The assumption of a freshwater deluge was removed from the model.

The AMOC appears to be less sensitive without the freshwater coming in.

Climate models that evaluate how the AMOC will respond to future increases of freshwater from ice melt are particularly important.

He says that the AMOC is built into many models and that it is caused by future global warming from increasing carbon dioxide in the atmosphere.

The consequences of a drastic weakening of the AMOC include rapid sea-level rise on the eastern coast of North America, cooling over Europe that could disrupt agriculture, and disruption of Asian monsoons. The new modeling study does not rule out abrupt change, but it does anticipate a much smaller reduction in AMOC strength.

The AMOC should be viewed with caution until the challenge is solved. It can change again.

More information: Feng He et al, Freshwater forcing of the Atlantic Meridional Overturning Circulation revisited, Nature Climate Change (2022). DOI: 10.1038/s41558-022-01328-2 Journal information: Nature Climate Change Citation: Melting ice caps may not shut down ocean current (2022, April 9) retrieved 9 April 2022 from https://phys.org/news/2022-04-ice-caps-ocean-current.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.