Scientists speculate about the future of Earth’s oceans covered in ice on their harsh fringes

Credit: Alessandro Toffoli, author provided

One of the harshest and most dynamic regions on Earth is marginal ice area– The place where ocean waves meet sea ice, which is formed by freezing of the ocean surface.

Published today, a topical issue of the magazine Philosophical Transactions of the Royal Society A It reviews the rapid progress that researchers have made over the past decade in understanding and modeling this challenging environment.

This research is vital for us to better understand the complex interactions of Earth’s climate systems. That’s because the marginal glacial area plays a role in the seasonal freezing and thawing of the oceans.

Hard place to study

In the Arctic and Antarctica, ocean surface temperatures are constantly dropping -2℃Cold enough to freeze to form a layer of sea ice.

At higher latitudes near the poles, sea ice forms a solid cover several meters thick on the ocean that reflects sunlight, cooling the area and driving Cold water around the oceans. This makes sea ice a major component of the climate system.

But at lower latitudes, as the ice-covered ocean transitions into the open ocean, sea ice forms into smaller, more mobile bits called “rafts” separated by water or a mass of ice crystals.

Drone footage from Canada shows the waves generated by a ship breaking continuous ice into a raft.

This marginal ice area interacts with the atmosphere above and the ocean below it in a very different way than the ice sheet closer to the poles.

It’s a challenging environment for scientists to work in, with a trip to the marginal ice region around Antarctica in 2017. Winds over 90 km/h And the Waves over 6.5 meters high. It’s also difficult to monitor from afar because the pontoons are smaller than most satellites can see.

Crushed by the waves

The marginal ice area also interacts with open perimeter Across surface waves, which travels from open water to the area, and affects the ice. The waves It can have a devastating effect on the ice sheet, by breaking up large rafts and making them more susceptible to melting during the summer.

By contrast, during the winter, waves can promote the formation of “pancake” rafts, so called because they are thin discs of sea ice (you can see them in the photo above).

But wave energy They lose themselves during interactions with buoys, such that the waves become progressively weaker as they move deeper into the marginal glacial region. This results in wave and ice feedback mechanisms driving the evolution of sea ice in a changing climate.

Scientists speculate about the future of Earth's oceans covered in ice on their harsh fringes

Two pictures of the ice cap before and during its breakup. Credit: Elie Dumas-Lefebvre / Université du Québec à Rimousk

For example, a trend to warmer temperatures will weaken the ice sheet, allowing waves to travel deeper into the ice-covered oceans and cause further splitting, weakening the ice sheet – and so on.

Scientists who study marginal ice zone dynamics aim to improve our understanding of the region’s role in the dramatic and often confusing changes that the world’s sea ice is undergoing in response to climate change.

For example, in the Arctic Ocean, sea ice cover has decreased “by about half since the 1980s”. In Antarctica, sea ice cover has recently had one of the largest and smallest extents on record, with the marginal ice area being one source of year-to-year fluctuations.

Our progress in better understanding these extreme regions has centered around large international research programs, run by the United States Office of Naval Research and others. These programs include earth scientists, geophysicists, oceanographers, engineers, and even applied mathematicians (like us).

Recent efforts have produced innovative observing techniques, such as a three-dimensional image wave method, buoyancy dynamics in the marginal ice area from aboard an icebreaker, and capturing waves in the ice from satellite images.

It also resulted in new models capable of simulating the interaction of waves and ice from a level Single rafts for the general behavior of full oceans. Australian developments prompted a multi-month, Australian-led experiment in the marginal ice region of Antarctica, on the new $500 million icebreaker. RSV NoinaWhich is expected next year.

Scientists speculate about the future of Earth's oceans covered in ice on their harsh fringes

Wave measurements in the fringe ice area imposed on the original images from aboard the SA Agulhas II. Credit: Alessandro Toffoli/University of Melbourne and Alberto Alberlo/University of East Anglia

The marginal ice area will be an increasingly important component of the world’s sea ice cover in the future, as temperatures rise and waves become more extreme.

Despite rapid progress, there is still some way to go before understanding feedback processes in the marginal ice zone is translated into improved climate predictions used by, for example, IPCC assessment reports.

Including the marginal ice area in climate models Described as the “holy grail” of the field by one of its leading figures, the issue of the topic points to closer links with the broader climate community as the field’s next major trend.

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