Meltwater lakes are accelerating glacier ice loss

Date:
October 9, 2020
Source:
University of Leeds
Summary:
Meltwater lakes that form at glacier margins cause ice to recede
much further and faster compared to glaciers that terminate on land,
according to a new study. But the effects of these glacial lakes are
not represented in current ice loss models, warn the study authors.

Therefore, estimates of recession rates and ice mass loss from lake-
terminating glaciers in the coming decades are likely to be under-
estimated.



FULL STORY ========================================================================== Meltwater lakes that form at glacier margins cause ice to recede much
further and faster compared to glaciers that terminate on land, according
to a new study. But the effects of these glacial lakes are not represented
in current ice loss models, warn the study authors.


========================================================================== Therefore, estimates of recession rates and ice mass loss from
lake-terminating glaciers in the coming decades are likely to be under-estimated.

Many mountain glaciers now terminate in such lakes, formed as meltwater
becomes trapped behind ridges of glacier debris. They are known as
proglacial lakes.

Climate change has increased glacier melt worldwide and this in turn
has led to a dramatic increase in the size and number of proglacial
lakes. But the effects of proglacial lakes on the rates of deglaciation
and on glacier behaviour have previously been poorly understood.

Now, an international team of researchers, led by the University of
Leeds, has quantified for the first time the influence of proglacial
lakes on mountain glaciers using computer simulations. They found that
the presence of a proglacial lake causes a glacier to recede more than
four times further and accelerate ice flow by up to eight times when
compared to the same glacier terminating on land under the same climate.

The findings, published today in the journal Geophysical Research Letters,
show that a land-terminating glacier took 1000 years to succumb to the
same amount of recession as a lake-terminating glacier experienced in
100 years.

Study lead author Dr Jenna Sutherland undertook this research while a
PhD candidate in the School of Geography at Leeds. She said: "An ice
cube in a bowl of water is going to melt much more quickly than an ice
cube sitting on a table, and the effect proglacial lakes have on glacier
ice is roughly the same.

"The simulations show that the influence of a proglacial lake on a glacier predominantly takes place over decades to centuries rather than over
millennia, meaning the glacier recedes much faster than it ever could
from climatic changes alone." Study co-author Dr Jonathan Carrivick,
a senior lecturer in geomorphology at Leeds, said: "Our findings suggest
that simulations of past, contemporary or future glaciers ignore the
effects of ice-contact lakes and will likely mis- represent the timing
and rate of recession, especially the changes to the timing and rate
that will occur once a proglacial lake forms.

"This effects need to be included in all future models and simulations
if we are to have an accurate global picture of glacial ice loss."
The team used the BISICLES ice-flow model, to analyse the effects of
a proglacial on the Pukaki Glacier, New Zealand, during recession from
the end of the last ice age.

Study co-author James Shulmeister from the University of Canterbury,
New Zealand said: "While this study focussed on New Zealand, proglacial
lakes are prevalent during glacial retreat worldwide and this paper should therefore be of global interest and importance." In addition, he noted:
"This study is also critical because the timing of ice retreat is often
used to determine the synchrony or lack thereof of in climate events
globally. Major inferences have been made about the roles of phenomena
like oceanic circulation in affecting the global climate system from
glacial retreat timings. If the timings are wrong, the relationship
between these processes may need to be re-examined."

========================================================================== Story Source: Materials provided by University_of_Leeds. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. J. L. Sutherland, J. L. Carrivick, N. Gandy, J. Shulmeister, D. J.

Quincey, S. L. Cornford. Proglacial Lakes Control Glacier Geometry
and Behavior During Recession. Geophysical Research Letters, 2020;
47 (19) DOI: 10.1029/2020GL088865 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201009114206.htm

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