Greenland is on track to lose ice faster than in any century over 12,000
years

Date:
September 30, 2020
Source:
University at Buffalo
Summary:
If human societies don't sharply curb emissions of greenhouse
gases, Greenland's rate of ice loss this century is likely to
greatly outpace that of any century over the past 12,000 years,
a new study concludes.

Scientists say the results reiterate the need for countries around
the world to take action now to reduce emissions, slow the decline
of ice sheets, and mitigate sea level rise.



FULL STORY ==========================================================================
If human societies don't sharply curb emissions of greenhouse gases, Greenland's rate of ice loss this century is likely to greatly outpace
that of any century over the past 12,000 years, a new study concludes.


==========================================================================
The research will be published on Sept. 30 in the journal Nature. The
study employs ice sheet modeling to understand the past, present
and future of the Greenland Ice Sheet. Scientists used new, detailed reconstructions of ancient climate to drive the model, and validated the
model against real-world measurements of the ice sheet's contemporary
and ancient size.

The findings place the ice sheet's modern decline in historical context, highlighting just how extreme and unusual projected losses for the 21st
century could be, researchers say.

"Basically, we've altered our planet so much that the rates of ice
sheet melt this century are on pace to be greater than anything we've
seen under natural variability of the ice sheet over the past 12,000
years. We'll blow that out of the water if we don't make severe reductions
to greenhouse gas emissions," says Jason Briner, PhD, professor of geology
in the University at Buffalo College of Arts and Sciences. Briner led the collaborative study, coordinating the work of scientists from multiple disciplines and institutions.

"If the world goes on a massive energy diet, in line with a scenario
that the Intergovernmental Panel on Climate Change calls RCP2.6, our
model predicts that the Greenland Ice Sheet's rate of mass loss this
century will be only slightly higher than anything experienced in the
past 12,000 years," Briner adds. "But, more worrisome, is that under a high-emissions RCP8.5 scenario -- the one the Greenland Ice Sheet is
now following -- the rate of mass loss could be about four times the
highest values experienced under natural climate variability over the
past 12,000 years." He and colleagues say the results reiterate the need
for countries around the world to take action now to reduce emissions,
slow the decline of ice sheets, and mitigate sea level rise. The research
was largely funded by the U.S.

National Science Foundation.



========================================================================== Combining ice sheet modeling with field work, real-life observations
The study brought together climate modelers, ice core scientists, remote sensing experts and paleoclimate researchers at UB, NASA's Jet Propulsion Laboratory (JPL), the University of Washington (UW), Columbia University's Lamont-Doherty Earth Observatory (LDEO), the University of California,
Irvine (UCI) and other institutions.

This multidisciplinary team used a state-of-the-art ice sheet model to
simulate changes to the southwestern sector of the Greenland Ice Sheet, starting from the beginning of the Holocene epoch some 12,000 years ago
and extending forward 80 years to 2100.

Scientists tested the model's accuracy by comparing results of the
model's simulations to historical evidence. The modeled results matched
up well with data tied to actual measurements of the ice sheet made by satellites and aerial surveys in recent decades, and with field work identifying the ice sheet's ancient boundaries.

Though the project focused on southwestern Greenland, research shows
that changes in the rates of ice loss there tend to correspond tightly
with changes across the entire ice sheet.



==========================================================================
"We relied on the same ice sheet model to simulate the past, the present
and the future," says co-author Jessica Badgeley, a PhD student in the UW Department of Earth and Space Sciences. "Thus, our comparisons of the ice
sheet mass change through these time periods are internally consistent,
which makes for a robust comparison between past and projected ice
sheet changes." "We have significantly improved our understanding of
how anomalous future Greenland change will be," says co-author Joshua
Cuzzone, PhD, an assistant project scientist at UCI who completed
much of his work on the study as a postdoctoral researcher at JPL and
UCI. "This work represents a massive success for multidisciplinary
science and collaboration, and represents a framework for future
successful multidisciplinary work." Cuzzone and other researchers at
UCI and JPL led ice sheet modeling, leveraging the work of colleagues
at UW, who used data from ice cores to create maps of temperatures and precipitation in the study region that were used to drive the ice sheet
model simulations up to the year 1850. Previously published climate data
was used to drive the simulations after that date.

UB and LDEO scientists partnered on field work that helped validate the
model by identifying the ice sheet's boundaries in southwestern Greenland thousands of years ago.

"We built an extremely detailed geologic history of how the margin of
the southwestern Greenland Ice Sheet moved through time by measuring beryllium-10 in boulders that sit on moraines," says co-author Nicola's
Young, PhD, associate research professor at LDEO. "Moraines are large
piles of debris that you can find on the landscape that mark the former
edge of an ice sheet or glacier. A beryllium-10 measurement tells you how
long that boulder and moraine have been sitting there, and therefore tells
you when the ice sheet was at that exact spot and deposited that boulder.

"Amazingly, the model reproduced the geologic reconstruction really
well. This gave us confidence that the ice sheet model was performing
well and giving us meaningful results. You can model anything you want
and your model will always spit out an answer, but we need some way to determine if the model is doing a good job." A continuous timeline
of changes to the Greenland Ice Sheet The study makes an important
contribution by creating a timeline of the past, present and future of
the Greenland Ice Sheet, Briner says. The results are sobering.

"We have long timelines of temperature change, past to present to future,
that show the influence of greenhouse gases on Earth's temperature,"
Briner says.

"And now, for the first time, we have a long timeline of the impacts
of that temperature -- in the form of Greenland Ice Sheet melt --
from the past to present to future. And what it shows is eye-opening."
"It is no secret that the Greenland Ice Sheet is in rough shape and is
losing ice at an increasing rate," Young says. "But if someone wants to
poke holes in this, they could simply ask, 'how do you know this isn't
just part of the ice sheet's natural variability?' Well, what our study suggests is that the rate of ice loss for this century will exceed the
rate of ice loss for any single century over the last 12,000 years. I
think this is the first time that the current health of the Greenland Ice
Sheet has been robustly placed into a long- term context." Despite these sobering results, one vital takeaway from the model's future projections
is that it's still possible for people and countries around the world to
make an important difference by cutting emissions, Briner says. Models of
the RCP2.6 and RCP8.5 scenarios yield very different results, with high- emission scenarios producing massive declines in the ice sheet's health,
and significant sea level rise.

"Our findings are yet another wake-up call, especially for countries
like the U.S.," Briner says. "Americans use more energy per person than
any other nation in the world. Our nation has produced more of the CO2
that resides in the atmosphere today than any other country. Americans
need to go on an energy diet. The most affluent Americans, who have
the highest energy footprint, can afford to make lifestyle changes,
fly less, install solar panels and drive an energy-efficient vehicle."
"This study shows that future ice loss is likely to be larger than
anything that the ice sheet experienced in the Holocene -- unless we
follow a low-carbon emission scenario in the future," Badgeley says.


========================================================================== Story Source: Materials provided by University_at_Buffalo. Original
written by Charlotte Hsu.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jason P. Briner, Joshua K. Cuzzone, Jessica A. Badgeley, Nicola's E.

Young, Eric J. Steig, Mathieu Morlighem, Nicole-Jeanne Schlegel,
Gregory J. Hakim, Joerg M. Schaefer, Jesse V. Johnson, Alia
J. Lesnek, Elizabeth K. Thomas, Estelle Allan, Ole Bennike,
Allison A. Cluett, Beata Csatho, Anne de Vernal, Jacob Downs,
Eric Larour, Sophie Nowicki. Rate of mass loss from the Greenland
Ice Sheet will exceed Holocene values this century. Nature, 2020;
586 (7827): 70 DOI: 10.1038/s41586-020-2742-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200930114209.htm

--- up 5 weeks, 2 days, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)