Strong tides, vanishing lakes may prove beneficial to Antarctic ice shelf

The lakes that form on the ice shelves can cause cracks in the ice, increasing the chance of ice shelf collapse and sea level rise. Researchers say that if meltwater accumulates in certain areas, it may temporarily fix the ice shelf.

The largest potential source of sea level rise is the ice inAntarctica. We need to understand what is happening to the ice shelves. We need to know where the water is and what it is doing to the ice shelves.

Trusel and his colleagues used satellite data to study a meltwater lake that forms annually at the Amery Ice Shelf. The ground line is where land ice transitions to a floating ice shelf that prevents it from flowing into the ocean and raising sea levels. The basin that could collect water is formed by the ice in this area.

The researchers found that strong tidal activity can cause the meltwater lake to drain quickly, often in as little as several days. The rapid draining stops water from spreading onto the ice shelf and raising the risk of collapse. The first observations of tides potentially forcing large-scale lake drainage were reported by the team.

The researchers used data from the satellites to measure and track changes to the lake during the austral summers. The Landsat 8 instruments can capture up to 11 bands of light, which is more than an ordinary camera can. The data can be used to map ice, water, snow and cloud cover.

A master's student in geography at Penn State, Zhuolai Pan, used Landsat images to calculate lake volume and create a time series that shows the lake forming and draining. The team used data from the radar sensors on the satellites to refine the time series. The instruments have a resolution of 33 feet and can see through clouds, which is important because the coast of Antarctica can often see more clouds than the sun.

The lake is 65 feet deep and contains almost 5 billion gallons of water, enough to fill over 7,000 swimming pools, according to the researchers.

It is not the biggest lake, but it is significant in terms of its size. A large volume of water is disappearing, and it happens almost every year.

Satellite imagery taken after a drainage event was examined by the researchers. The images showed the lake bottom, where the team found a large crater, ice blocks and a large fracture. The water most likely drained through the ice at 2,000 feet.

This is the most detailed view of a freshly drained lake that we have ever had, and it was only previously seen on the much warmer and wetter Greenland Ice Sheet.

Drainage events occur at least once a year with sufficient observations. The researchers think that strong tidal activity, instead of water volume, was the reason for the drainage at different lake volumes and depths.

When the Earth, moon and sun align, Earth experiences stronger tidal activity. Ice shelves are subject to tidal activity because they float in the ocean. The base of the ice can be stressed by higher high tides, which could cause a break. Lower low tides force the ice shelf to flex downward, transferring stresses to the surface of the ice and potentially extending the break. The weight of the water at the surface could cause the ice shelf to break and cause an opening to drain the lake.

The ice is acting like a door hinge, with stresses occurring at the top and bottom of the ice.

Scientists think that water at the surface is a sign of ice shelf collapse. They observed the collapse of the ice shelf. Pan said that earlier Landsat data shows the lake forming as far back as the 1970s. The same lakes that dot the ice shelf are in aerial photographs taken by the U.S. Navy during World War II.

The water has been around for a long time, and so there are more nuances to it. We need to know how it affects ice shelf stability.

The scientists will investigate whether other lakes in the region drain due to tidal activity. The current study raises many questions, but it is the latest step to better understand ice shelf stability and how fast seas will rise in the future.

At the National Snow and Ice Data Center, where she was a researcher, and now at General GM, she contributed to the study.

More information: Luke D. Trusel et al, Repeated Tidally Induced Hydrofracture of a Supraglacial Lake at the Amery Ice Shelf Grounding Zone, Geophysical Research Letters (2022). DOI: 10.1029/2021GL095661 Journal information: Geophysical Research Letters Citation: Strong tides, vanishing lakes may prove beneficial to Antarctic ice shelf (2022, April 19) retrieved 19 April 2022 from https://phys.org/news/2022-04-strong-tides-lakes-beneficial-antarctic.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.