Widespread retreat and loss of marine-terminating glaciers in the
northern hemisphere

Date:
January 31, 2022
Source:
University of Ottawa
Summary:
Researchers have mapped out all the glaciers that end in the ocean
in the Northern Hemisphere and provide a measure of their rate of
change over the last 20 years. Their findings will help us better
understand -- and perhaps predict -- the impact of climate change
north of the equator.



FULL STORY ========================================================================== Researchers have mapped out all the glaciers that end in the ocean in
the Northern Hemisphere and provide a measure of their rate of change
over the last 20 years. Their findings will help us better understand --
and perhaps predict -- the impact of climate change north of the equator.


==========================================================================
In their article "Retreat of Northern Hemisphere marine-terminating
glaciers, 2000-2020" published in Geophysical Research Letters, they
analyzed all 1704 glaciers that touched the ocean in the year 2000 and documented their frontal position in 2000, 2010, and in 2020.

Chilling findings "Since 2000, glaciers in the Northern Hemisphere that
end in the ocean lost a total area of 390 km2 per year. That's 6.6 times
the area of Manhattan, or an average of more than 1 km2 per day," said
lead author Will Kochtitzky, PhD candidate in the Department of Geography, Environment and Geomatics at the University of Ottawa.

According to the study, glaciers flowing from the Greenland Ice Sheet
accounted for over 60% of total area losses.

"Of the 1704 glaciers that ended in the ocean in the year 2000, a
total of 123 of them no longer met the ocean in 2020 due to retreat,"
said Kochtitzky.



========================================================================== "Overall, we found that 85% of glaciers retreated, 12% did not change
within uncertainty limits, and only 3% of glaciers advanced from 2000 to
2020." Global warming While climate change induced by human activities
is broadly responsible for melting ice caps and shrinking glaciers
around the world, local topographic and environmental conditions are
important in explaining why some glaciers retreated more than others,
according to the researchers.

"We found large variations in glacier response to similar changes in air
and ocean temperature and sea ice concentrations, showing that unique
glacier characteristics are the most important factor in controlling
the variability of glacier retreat," explained co-author Luke Copland,
Full Professor in the Department of Geography, Environment and Geomatics
at the University of Ottawa, and University Research Chair in Glaciology.

"The loss of ice shelves across the Arctic is one of the main drivers
of retreat," he added. "Glaciers which have an unusually wide margin
where they meet the ocean, and those that have a bed below sea level
and which gets deeper away from the coast, also saw particularly fast
retreat rates." Of the few glaciers that defied the odds and advanced
instead of retreating, most were due to "internal instabilities called
surge events," which cause the glacier to move 10 to 100 times faster
than normal for a few years.



========================================================================== "However, glaciers that displayed large advances due to surging over the
past decade are likely to experience large retreats in the next few years,
with overall retreat in the long term," said Kochtitzky.

The two researchers manually examined satellite imagery at the University
of Ottawa to map the glaciers and measure the retreating.

"Prior to this study, we didn't even know how many glaciers reached the
ocean in the Northern Hemisphere, let alone understand how or why they
were changing," said Will Kochtitzky.

"This study has mapped every such glacier for the first time, and
from this provided the first measure of their rates of change. This
information is crucial for understanding the impacts of climate change on
a hemispheric basis and will be used in future climate assessment reports
such as those issued by the Intergovernmental Panel on Climate Change
(IPCC)." Too late to turn the tide? According to uOttawa researchers, marine-terminating glacier losses are widespread across the Northern Hemisphere, and there is little likelihood that these losses will slow
down under the current climate regime.

"We have lost at least a dozen ice shelves over the past 20 years because
a climate threshold has been reached beyond which these ice masses can
no longer survive," said Dr. Luke Copland.

"The few remaining ice shelves in northern Canada, Greenland,
and Russia are likely to disappear in the coming decades." ========================================================================== Story Source: Materials provided by University_of_Ottawa. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
* Retreating_glaciers ========================================================================== Journal Reference:
1. William Kochtitzky, Luke Copland. Retreat of Northern Hemisphere
Marine‐Terminating Glaciers, 2000-2020. Geophysical Research
Letters, 2022; 49 (3) DOI: 10.1029/2021GL096501 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220131132814.htm

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