Hidden Ocean Under Antarctica Is Affecting Global Sea Level Rise In Mysterious Ways

It is an established fact that Antarctica¡¯s ice shelves - large extensions of the ice on land that float on tides - melt from below as the ocean¡¯s warm up.

However, there is very little data available about how the new-formed water mixes underneath the ice. Scientists have now managed to measure the same.

Reuters

A new study sheds light on the role of ocean currents in the melting in Antarctica, one of the largest uncertainties in climate model predictions. The continent is known to have hidden ocean cavities which are important to assess the future rise in sea level.

The Ross Ice Shelf is one such floating slab of ice in Antarctica, considered to be the largest on Earth at 480,000 square kilometres. The ocean cavity concealed by it spans 700km south from Antarctica's coast. Scientists have now measured the impact of ocean currents on the same.

Antarctic oceanic study

Antarctica (Representative Image: Reuters)

Ross Ice Shelf has largely been unexplored to date. Apart from the recent research, the only other expedition to the ocean cavity underneath it dates back to the 1970s. At the time, scientists were able to figure out that the ocean cavity was not a static bathtub. Instead, it had layers of varying water masses, with different temperatures and salinities.

Though subsequent studies have been conducted from the edges or from above of such ice shelves, measurements from directly below the ice layers were needed to really understand how the melting of ice affects the system.

Extension to 2017 experiment

In 2017, author of a report on The Conversation claims to have used a hot-water jet on a British Antarctic Survey design, in order to drill through 350 meters of ice to the ocean below. The team was able to make detailed ocean measurements. It even left some of the instruments behind to continue monitoring ocean currents and temperature. More data is still coming in via satellite.

The team discovered that the hidden ocean below the ice shelf acts like a massive estuary with comparatively warm (by 2¡æ) seawater coming in at the seabed. The warm seawater is able to ¡±cycle close to the surface in a combination of meltwater and sub-glacial freshwater squeezed out from the ice sheet and Antarctica's hidden rocky foundation.¡±

Though the ice shelves protect such ocean cavities from furious winds and freezing air temperatures of Antarctica, there is no way to stop the tides. The new data now suggests tides are responsible for pushing the hidden ocean cavity back and forth past and mix parts of the ocean cavity.

Since the process works on a daily basis, scientists now deal with the puzzle of accounting for them in projections over centuries. Since the data proves that the daily changes can add up, finding a solution to the issue is a matter of concern.

Antarctica's climate change impact

(Representative Image: Reuters)

The new data indicates that any given parcel of water spends one to three years (previously thought to be 6 years) in making its way through the cavity. This is critical in understanding the role of these ice shelves in the sea level rise over the next few centuries.

Research indicates that a rise of more than 2¡ãC atmospheric temperature will cause major Antarctic ice shelves to collapse and further add to the sea level rise. With the same temperature rise, the sea level can rise by up to 3 meters by 2300, warns the report.