Emissions could add 15 inches to 2100 sea level rise

Date:
September 17, 2020
Source:
NASA/Goddard Space Flight Center
Summary:
An international effort that brought together more than 60 ice,
ocean and atmosphere scientists from three dozen international
institutions has generated new estimates of how much of an impact
Earth's melting ice sheets.



FULL STORY ==========================================================================
An international effort that brought together more than 60 ice, ocean
and atmosphere scientists from three dozen international institutions
has generated new estimates of how much of an impact Earth's melting
ice sheets could have on global sea levels by 2100. If greenhouse gas
emissions continue apace, Greenland and Antarctica's ice sheets could
together contribute more than 15 inches (38 centimeters) of global sea
level rise -- and that's beyond the amount that has already been set in
motion by Earth's warming climate.


==========================================================================
The results point to a greater range of possibilities, from ice sheet
change that decreases sea level by 3.1 in (7.8 cm), to increasing it
by 12 in (30 cm) by 2100, with different climate scenarios and climate
model inputs. The regional projections show the greatest loss in West Antarctica, responsible for up to 7.1 in (18 cm) of sea level rise by
2100 in the warmest conditions, according to the research.

"The Amundsen Sea region in West Antarctica and Wilkes Land in
East Antarctica are the two regions most sensitive to warming ocean temperatures and changing currents, and will continue to lose large
amounts of ice," said He?le?ne Seroussi, an ice scientist at NASA's Jet Propulsion Laboratory in Southern California. Seroussi led the Antarctic
ice sheet modeling in the ISMIP6 effort.

"With these new results, we can focus our efforts in the correct
direction and know what needs to be worked on to continue improving
the projections." Different groups within the ISMIP6 community are
working on various aspects of the ice sheet modeling effort. All are
designed to better understand why the ice sheets are changing and to
improve estimates of how much ice sheets will contribute to sea level
rise. Other recent ISMIP6 studies include:
* How historical conditions and warming ocean temperatures that melt
floating ice shelves from below play a significant role in Antarctic
ice loss? (Reese et al, 2020)
* How sudden and sustained collapse of the floating ice shelves
impact the
Antarctic ice sheet as a whole? (Sun et al., 2020)
* How to convert large scale climate output into local conditions
that ice
sheet models can use? (Barthel et al, 2020; Slater et al; 2019,
2020; Nowicki et al., 2020, and Jourdain et al., 2020)
"It took over six years of workshops and teleconferences with scientists
from around the world working on ice sheet, atmosphere, and ocean
modeling to build a community that was able to ultimately improve our
sea level rise projections," Nowicki said. "The reason it worked is
because the polar community is small, and we're all very keen on getting
this problem of future sea level right. We need to know these numbers."
The new results will help inform the Sixth IPCC report scheduled for
release in 2022.



========================================================================== Results from this effort are in line with projections in the
Intergovernmental Panel on Climate Change's (IPCC) 2019 Special Report on Oceans and the Cryosphere. Meltwater from ice sheets contribute about a
third of the total global sea level rise. The IPCC report projected that Greenland would contribute 3.1 to 10.6 inches (8 to 27 cm) to global sea
level rise between 2000-2100 and Antarctica could contribute 1.2 to 11
inches (3 to 28 cm).

These new results, published this week in a special issue of the journal
The Cryosphere, come from the Ice Sheet Model Intercomparison Project
(ISMIP6) led by NASA's Goddard Space Flight Center in Greenbelt,
Maryland. The study is one of many efforts scientists are involved
in to project the impact of a warming climate on melting ice sheets,
understand its causes and track sea level rise.

"One of the biggest uncertainties when it comes to how much sea level
will rise in the future is how much the ice sheets will contribute,"
said project leader and ice scientist Sophie Nowicki, now at the
University at Buffalo, and formerly at NASA Goddard. "And how much the
ice sheets contribute is really dependent on what the climate will do."
"The strength of ISMIP6 was to bring together most of the ice sheet
modeling groups around the world, and then connect with other communities
of ocean and atmospheric modelers as well, to better understand what
could happen to the ice sheets," said Heiko Goelzer, a scientist from
Utrecht University in the Netherlands, now at NORCE Norwegian Research
Centre in Norway. Goelzer led the Greenland ice sheet ISMIP6 effort.

With warming air temperatures melting the surface of the ice sheet, and
warming ocean temperatures causing ocean-terminating glaciers to retreat, Greenland's ice sheet is a significant contributor to sea level rise. The ISMIP6 team investigated two different scenarios the IPCC has set for
future climate to predict sea level rise between 2015 and 2100: one with
carbon emissions increasing rapidly and another with lower emissions.

In the high emissions scenario, they found that the Greenland ice sheet
would lead to an additional global sea level rise of about 3.5 inches
(9 cm) by 2100.

In the lower emissions scenario, the loss from the ice sheet would
raise global sea level by about 1.3 inches (3 cm). This is beyond what is already destined to be lost from the ice sheet due to warming temperatures between pre- industrial times and now; previous studies have estimated
that 'locked in' contribution to global sea level rise by 2100 to be
about a quarter-inch (6 millimeters) for the Greenland ice sheet.

The ISMIP6 team also analyzed the Antarctic ice sheet to understand how
much ice melt from future climate change would add to sea level rise,
beyond what recent warming temperatures have already put in motion. Ice
loss from the Antarctic ice sheet is more difficult to predict: In the
west, warm ocean currents erode the bottom of large floating ice shelves, causing loss; while the vast East Antarctic ice sheet can gain mass,
as warmer temperatures cause increased snowfall.


========================================================================== Story Source: Materials provided
by NASA/Goddard_Space_Flight_Center. Original written by Kate
Ramsayer. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. He'le`ne Seroussi, Sophie Nowicki, Antony J. Payne, Heiko Goelzer,
William H. Lipscomb, Ayako Abe-Ouchi, Ce'cile Agosta, Torsten
Albrecht, Xylar Asay-Davis, Alice Barthel, Reinhard Calov,
Richard Cullather, Christophe Dumas, Benjamin K. Galton-Fenzi,
Rupert Gladstone, Nicholas R.

Golledge, Jonathan M. Gregory, Ralf Greve, Tore Hattermann,
Matthew J.

Hoffman, Angelika Humbert, Philippe Huybrechts, Nicolas C. Jourdain,
Thomas Kleiner, Eric Larour, Gunter R. Leguy, Daniel P. Lowry,
Chistopher M. Little, Mathieu Morlighem, Frank Pattyn, Tyler Pelle,
Stephen F.

Price, Aure'lien Quiquet, Ronja Reese, Nicole-Jeanne Schlegel,
Andrew Shepherd, Erika Simon, Robin S. Smith, Fiammetta Straneo,
Sainan Sun, Luke D. Trusel, Jonas Van Breedam, Roderik S. W. van
de Wal, Ricarda Winkelmann, Chen Zhao, Tong Zhang, Thomas
Zwinger. ISMIP6 Antarctica: a multi-model ensemble of the Antarctic
ice sheet evolution over the 21st century. The Cryosphere, 2020;
14 (9): 3033 DOI: 10.5194/tc-14-3033-2020 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200917122844.htm

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