Hexbyte Glen Cove NASA finds 2021 Arctic summer sea ice 12th-lowest on record thumbnail

Hexbyte Glen Cove NASA finds 2021 Arctic summer sea ice 12th-lowest on record

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A still image visualizing Arctic sea ice on Sept. 16, 2021, when the ice appeared to reach its yearly minimum extent. On this date, the extent of the ice was 4.72 million square miles (1.82 million square kilometers). Credit: NASA’s Scientific Visualization Studio

Sea ice in the Arctic appears to have hit its annual minimum extent on Sept. 16, after waning in the 2021 Northern Hemisphere spring and summer. The summertime extent is the 12th-lowest in the satellite record, according to scientists at the NASA-supported National Snow and Ice Data Center and NASA.

This year, the minimum extent of Arctic sea ice dropped to 4.72 million square kilometers (1.82 million square miles). Sea ice extent is defined as the total area in which ice concentration is at least 15%.

The average September minimum extent record shows significant declines since satellites began measuring consistently in 1978. The last 15 years (2007 to 2021) are the lowest 15 minimum extents in the 43-year record.






On Sept. 16, 2021, Arctic sea ice reached its minimum summertime extent. Credit: NASA’s Goddard Space Flight Center/Scientific Visualization Studio

This visualization, created at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, shows data provided by the Japan Aerospace Exploration Agency (JAXA), acquired by the Advanced Microwave Scanning Radiometer 2 (AMSR2) instrument aboard JAXA’s Global Change Observation Mission 1st-Water “SHIZUKU” (GCOM-W1) satellite.



Citation:
NASA finds 2021 Arctic summer sea ice 12th-lowest on record (2021, September 22)
retrieved 23 September 2021
from https://phys.org/news/2021-09-nasa-arctic-summer-sea-ice.html

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Hexbyte Glen Cove Mystery of glacial lake floods solved thumbnail

Hexbyte Glen Cove Mystery of glacial lake floods solved

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The hot water drill used to drill through the glacier to the subglacial lakes. The drill stem is hundreds of meters below in the ice, suspended on a rubber hose through which hot water is pumped down. Credit: Eric Gaidos

A long-standing mystery in the study of glaciers was recently —- and serendipitously—solved by a team led by University of Hawai’i at Mānoa astrobiologist and earth scientist Eric Gaidos. Their findings were published this week in the journal Geophysical Research Letters.

The mystery involves floods or “jokulhlaups” that emerge suddenly and unpredictably from or like those in Iceland where volcanic heat melts the ice and accumulates in lakes underneath the glaciers. Scientists have long studied the development of these floods, which are some of the largest on Earth.

“These floods may affect the motion of some glaciers and are a significant hazard in Iceland,” said Gaidos, professor at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). “But the mechanism and timing of the initiation of these floods has not been understood.”

Then, in June 2015, an unexpected series of events revealed how these floods start.

That summer, Gaidos and colleagues drilled a hole to one of the Icelandic lakes to study its microbial life. While collecting samples through the borehole, the team noticed a downwards current, like a bathtub drain, in the hole.

“The flow was so strong we nearly lost our sensors and sampling equipment into the hole,” said Gaidos. “We surmised that we had accidentally connected a inside the glacier to the beneath. That water mass was rapidly draining into the lake.”

Illustration of the water movement that may have triggered the flood of June 2015 (arrows indicate flow direction): the subglacial lake, warmed to 4 C by geothermal input, the perched reservoir fed by summer melt through the firn layer, a water-filled system of crevasses and conduits (moulins), our borehole, and the outlet under the ice dam. Credit: Gaidos, et al. (2020)

A few days later, after the team had left the glacier, the lake drained in a . Fortunately, the flood was small and Icelanders have an elaborate early-warning system on their rivers so no people were hurt, nor infrastructure damaged in this event, Gaidos assured.

The researchers used a computer model of the draining of the flow through the hole , and its effect on the lake, to show that this could have triggered the flood.

“We discovered that the glacier can contain smaller bodies of water above the lakes fed by summer melting,” said Gaidos. “If this water body is hydraulically connected to the lake then the pressure in the lake rises and that allows water to start draining out underneath the glacier.”

In June 2015, a team led by Gaidos used hot water to melt a hole through 250 meters of ice to sample a lake beneath a glacier in Iceland. Credit: Eric Gaidos

While the team made an artificial connection to the lake in 2015, natural connections can form when water from rain or melting snow accumulates in crevasses and the pressure eventually forces a crack through the glacier to the lake. This discovery provides a new understanding of how these floods can start and how this depends on weather and the season.

Collaborators in Iceland are continuing to research this phenomenon using radio echo-sounding to search for water bodies within the ice, as well as study the larger lake below it.



More information:
E. Gaidos et al, Après Nous, le Déluge: A Human‐Triggered Jökulhlaup from a Subglacial Lake, Geophysical Research Letters (2020). DOI: 10.1029/2020GL089876

Citation:
Mystery of glacial lake floods solved (2020, November 7)
retrieved 8 November 2020
from https://phys.org/news/2020-11-mystery-glacial-lake.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.