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Existing Climate Model Simulations Overrate Sea-Level Rise in Future

The Antarctic ice sheet’s melting rate is primarily regulated by the rise of ocean temperatures around Antarctica.

Existing Climate Model Simulations Overrate Sea-Level Rise in Future

Image Credit: Attapol Yiemsiriwut/shutterstock.com

Researchers from Utrecht University have employed a new, higher resolution climate model simulation and discovered a very gradual increase in ocean temperature than that of the present simulations with a coarser resolution.

As a result, the predicted sea-level increase in 100 years is around 25% lower compared to what is anticipated from the current simulations. The findings of the study were published in the Science Advances journal.

Predictions on the future sea-level increase are dependent on a huge ensemble of climate model simulations. The output from such simulations enables comprehending climate change in the future and its impacts on the sea level.

The constant goal of climate scientists is to enhance such models, for instance, by making use of a much greater spatial resolution that considers more information.

High-resolution simulations can determine the ocean circulation much more accurately,” stated Professor Henk Dijkstra who, along with his PhD candidate René van Westen, has been investigating ocean currents in high-resolution climate model simulations in recent years.

Ocean Eddies

The new high resolution model considers ocean eddy processes for its estimates. An eddy is a huge (10 to 200 km) turbulent and swirling feature that occurs in the ocean circulation. This feature serves as a contributor to the transport of heat and salt.

The addition of ocean eddies into the simulation results in a more sensible representation of the ocean temperatures around Antarctica, which is a main factor for finding the huge loss of the Antarctic ice sheet.

The Antarctic ice sheet is surrounded by ice shelves which reduce the flow of land ice into the ocean. Higher ocean temperatures around Antarctica increase the melting of these ice shelves, resulting in an acceleration of land ice into the ocean and consequently leading to more sea-level rise.

René van Westen, PhD Candidate, Utrecht University

The existing climate model simulations, which do not consider ocean eddies, estimate that the ocean temperatures surrounding Antarctica are rising under climate change. The new high resolution simulation exhibits very different behavior and a few regions near Antarctica even tend to cool under climate change.

These regions appear to be more resilient under climate change.

René van Westen, PhD Candidate, Utrecht University

Dijkstra added, “One obtains a very different temperature response due to ocean-eddy effects.”

Supercomputer

The latest high resolution model predicts a smaller mass due to ice-shelf melt: only a third than the present climate models. This decreases the predicted global sea-level increase by 25% in the next 100 years, noted Van Westen.

Although sea levels will continue to rise, this is good news for low-lying regions. In our simulation, ocean eddies play a crucial role in sea-level projections, showing that these small-scale ocean features can have a global effect,” added Van Westen

The researchers needed almost a year to complete the simulation of the high resolution model on the national supercomputer at SURFsara in Amsterdam.

These high-resolution models require an immense amount of computation, but are valuable as they reveal smaller-scale physical processes which should be taken into account when studying climate change.

Henk Dijkstra, Professor of Dynamical Oceanography, Utrecht University

HR CESM vs LR CESM

Video Credit: Utrecht University.

Journal Reference:

Van Westen, R M & Dijkstra, H A (2021) Ocean eddies strongly affect global mean sea-level projections. Science Advances. doi.org/10.1126/sciadv.abf1674.

Source: https://www.uu.nl/en

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