Increased meltwater influx from the glaciers of Antarctica are considered one of the most pressing consequences of climate change on the Southern Ocean. However, the fate meltwater which flows out from underneath the glaciers was unknown until now. An international team of researchers has discovered why this fresh water is often detected below the surface of the ocean, rather than rising to the top above denser seawater. The team found that the Earth’s rotation influences the way meltwater behaves – keeping it at depths of several hundred metres.

Most of the visible coastline of Antarctica consists of glaciers flowing into the Southern Ocean. Most of the meltwater runs off underneath the water line and stays in the deep according to the researchers. Picture: Michael Wenger
Most of the visible coastline of Antarctica consists of glaciers flowing into the Southern Ocean. Most of the meltwater runs off underneath the water line and stays in the deep according to the researchers. Picture: Michael Wenger

The research, led by the University of Southampton, is published this week in the journal Nature in association with colleagues at the National Oceanography Centre, Southampton, University of East Anglia (UEA), British Antarctic Survey and Stockholm University. The team found that Earth's rotation influences the way meltwater behaves -- keeping it at depths of several hundred metres. Professor Alberto Naveira Garabato, of Ocean and Earth Science at the University of Southampton and lead author of the study, says: "We believe our study is an important step in understanding how the meltwater mixes in the ocean and will help with the design of climate models, which largely assume meltwater is only present on the surface of oceans. Our research emphasizes its detection at greater depths and explains why it is found there." The scientists discovered the meltwater ends up settling hundreds of metres down, because as it tries to rise above the surrounding denser seawater, it is affected by Earth's rotation. This makes it spin very quickly around its vertical axis, resulting in the ejection of meltwater filaments in a sideways motion into the surrounding sea -- preventing the water from rising to the surface.

The study, which was conducted on a voyage on board of BAS ship James Clark Ross, used high precision instruments to measure even the faintest turbulences in the water. Credit: University of Southampton
The study, which was conducted on a voyage on board of BAS ship James Clark Ross, used high precision instruments to measure even the faintest turbulences in the water. Credit: University of Southampton

Scientists are interested in the depth at which water from Antarctic ice sheets enters the ocean because it has differing effects on global ocean circulation and climate. Surface meltwater makes the upper layers of the Southern Ocean lighter. This is thought to slow down the sinking of those waters in the region, and to favour the expansion of Antarctic sea ice. Injecting the same meltwater at depth is believed to have the opposite effect, favouring sinking of surface waters and the retreat of Antarctic sea ice. Dr Alexander Forryan, also of the University of Southampton, comments: "The effect of meltwater on climate was taken to the extreme and popularised in the Hollywood blockbuster 'The Day After Tomorrow'. While no one expects our climate to change in the space of a few days, like the movie -- we do know that fresh water flowing into our seas could dramatically affect sea levels and ocean circulation. As such, it is vital our models take into account the presence of both surface and deep meltwater to maximise their accuracy." The team now hope to develop a way to represent the process in climate models, so that climate modellers can reliably investigate the impact of the melting of Antarctica on our changing climate.

The British Antarctic Survey research and supply ship James Clark Ross has been in service since 1991 and is well-equipped for research voyages. It operates both in the Arctic and Antarctic. Credit: Tom-LC Wikipedia
The British Antarctic Survey research and supply ship James Clark Ross has been in service since 1991 and is well-equipped for research voyages. It operates both in the Arctic and Antarctic. Credit: Tom-LC Wikipedia

Source: University of Southampton