Meltwater is a driving force behind disappearing glaciers

Antarctic seals are providing new insight into why glaciers are disappearing. A study from the University of East Anglia reveals that an unexpectedly large amount of meltwater is modifying the climate and preventing sea ice from forming.

For the investigation, the researchers attached instruments to the heads of seals living near Pine Island Glacier in the remote Amundsen Sea west of Antarctica. This allowed the scientists to capture full-depth glacial meltwater observations in winter for the first time. 

The data collected by the tagged seals was used to measure water temperature and salinity. The experts found that meltwater distribution was highly variable with two primary layers – one in the upper 250 meters and another at around 450 meters deep. These two layers were connected by meltwater-rich columns. 

The meltwater provides near-surface heat that promotes areas of open water that are close to glaciers. The warmer water accelerates the melting rate of the ice shelves. 

“The temperature and salinity of water change everywhere glacial meltwater exists. Just like looking for a ‘fingerprint’ of glacial meltwater, we use temperature and salinity data to track the glacial meltwater,” said study lead author Yixi Zheng.

“The glacial meltwater distribution is very patchy. It doesn’t mix well with the ambient water, instead flowing along two meltwater-rich layers in the upper 250 meters and at around 450 meters, connected by meltwater-rich columns.”

“As the glacial meltwater is warmer and fresher than the ambient water, it is lighter than the ambient water and more likely to rise up. It brings heat and nutrients such as iron to the near surface, which may melt the sea ice near glaciers and increase the nutrient level near the surface. This enhances the air-sea interactions, and the meltwater-related nutrients may boost the growth of marine planktons like algae.”

The wintertime ocean processes described in the study are likely responsible for bringing nutrients to the near-surface layer prior to the spring bloom, and for bringing heat to the surface that prevents sea ice from forming. As a result, open areas of water near glaciers expand and persist.

Many glaciers around Antarctica are rapidly shrinking, and this is primarily due to melting that occurs at the interface between the ocean and the ice shelf glacier, or basal melting. The strongest melt has been reported in glaciers in west Antarctica.

According to the experts, further research is needed considering that the study was based on one year of seal-tag data from Pine Island Glacier, and it can’t be used to calculate trends over time.

The study is published in the journal Communications Earth and Environment.

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By Chrissy Sexton, Earth.com Staff Writer