Scientists dive deep into the future of Earth’s ice-covered oceans

By Al Mayadeen English
Source: Agencies
12 Sep 2022 13:26

In an effort to understand the complex interactions of Earth’s climate systems, scientists are diving into the ice-covered oceans.

Melting glaciers have changed the Earth’s axis. (Getty Images)

The marginal ice zone - where ocean waves meet sea ice generated by freezing of the ocean's surface - is one of the harshest and most dynamic areas on Earth.

A thematic issue of the journal Philosophical Transactions of the Royal Society A, published today, examines the rapid progress academics have achieved in understanding and modeling this complex environment over the last decade.

The research is important to better understand Earth's climate system interactions, due to the marginal ice zone's role in the seasonal freezing and thawing of oceans.

Harsh area to study

Surface ocean temperatures in the Arctic and Antarctic are consistently below -2°C - cold enough to freeze and generate a covering of sea ice.

Sea ice forms a solid, several-meter-thick cap on the ocean near the poles, reflecting the sun's rays and chilling the region while moving cool water around the oceans. As a result, sea ice is an important component of the climate system.

However, at lower latitudes, as the ice-covered ocean transitions to the open ocean, the sea ice forms into smaller, much more mobile chunks called “floes” that are separated by water or a slurry of ice crystals.

The marginal ice zone then interacts with the atmosphere above and below the ocean in a very different way to cover ice closer to the poles.

It's a difficult environment for scientists to work in, with winds exceeding 90km/h and waves exceeding 6.5m high on a 2017 cruise into the marginal ice zone around Antarctica. It is also difficult to observe remotely since the floes are too tiny to be seen by most satellites.

Crushed by waves

Surface waves, which migrate from the open ocean into the zone and damage the ice, also interact with the marginal ice zone. The waves can devastate the ice cover by breaking up massive floes and making them more vulnerable to melting over the summer.

In contrast, waves during winter can promote the formation of “pancake” floes, so-called because they are thin disks of sea ice. However, because wave energy is lost during contact with floes, waves steadily weaken as they go further into the marginal ice zone. In a changing climate, this results in wave-ice feedback mechanisms that drive sea ice evolution.

For example, a trend for warmer temperatures will weaken the ice cover, allowing waves to travel deeper into ice-covered oceans and cause more breakup, which further weakens the ice cover – and so on.

Scientists investigating marginal ice zone dynamics want to gain a better understanding of the zone's role in the dramatic and often baffling changes occurring in the world's sea ice as a result of climate change.