“Climate
breakdown has begun”
[U.N.
Secretary-General Antonio Guterres, 6 September 2023]
NOAA
Research, Global
ocean roiled by marine heatwaves, with more on the way,
28 June 2023, excerpts:
This
map depicts predicted marine heatwave conditions in September 2023 as
generated by the Physical Sciences Laboratory’s experimental
forecast model.
Credit:
NOAA Physical Sciences Laboratory. *Click on image to enlarge*
The
experimental forecast, which tracks the NOAA Climate Prediction
Center’s official outlook, is based on a large ensemble of climate
model predictions spanning June 2023 through May 2024….
A
marine heatwave is defined as a monthly regional sea surface
temperature anomaly that ranks in the top 10% of warmest months
compared with the 1991–2020 average. Long-term ocean warming trends
also contribute to unusually high ocean temperatures, but even with
the effects of long-term warming removed, models predict 25% of the
global ocean will experience sharp upward departures from more recent
conditions by September…..
In
this scenario it appears that the Southern Ocean waters are within a
probability range of between 60-80 per cent for the occurrence of
marine heatwave which might have also lead to a rise in Antarctic sea
surface temperatures.
Which
begs the questions:
How
will the over
60km long Halloween
Crack
in west
Antarctica
react to any additional stressors on the Brunt Ice
Shelf?
Will
the East
Coast Ice Sheet
which is said to contain four fifths of the world’s ice again
lose ice shelf through
iceberg calving as it did with
C-37 (144
sq.km) &
C-38 (415
sq. km) in
March 2022?
Just
how big are these Anthropocene Age icebergs going to grow – given many are the size of cities already? and
How long does the Southern Hemisphere have before sea level rise beyond the Antarctic Circle increases exponentially past millimetres into metres?
BACKGROUND
NASA
Earth Observatory, retrieved
from website 7 September 2023:
Antarctica’sBrunt Ice Shelf Finally Breaks
January
24, 2023
In
February 2019, a rift spanning most of the Brunt Ice Shelf in
Antarctica appeared ready to spawn an iceberg about twice the size of
New York City. The question among scientists was not if the growing
rift would finish traversing the shelf and break, but when? Now,
nearly four years later, it has done just that.
According
to the British Antarctic Survey (BAS), the break occurred late on
January 22, 2023, and produced a new iceberg with an area of 1550
square kilometers (about 600 square miles). The U.S. National Ice
Center has named it Iceberg A-81.
The berg is visible in this image, acquired on January 24, 2023, with
the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s
Terra satellite.
The
glacial ice in the shelf flows away from the interior of Antarctica
and floats on the eastern Weddell Sea. (For reference, the Antarctic
Peninsula and its ice shelves are located on the opposite side of the
Weddell.) The shelf has long been home to the British Antarctic
Survey’s Halley Research Station, where scientists study Earth,
atmospheric, and space weather processes. BAS reported that the
station, which was relocated farther inland in 2016 as the chasm
widened, was unaffected by the recent break.
January
12, 2021
The
break occurred along a rift known as Chasm
1. This chasm started growing in the 1970s, followed by a
period of dormancy, and then resumed growth in 2012. It continued to
lengthen for almost a decade, extending by as much as 4 kilometers
(2.5 miles) per year in early 2019. But even this growth spurt
slowed. That is, until the 2022–2023 Antarctic summer when the
chasm sped up and ultimately broke past the McDonald Ice Rumples—a
submerged knob of bedrock that served as a pinning point for this
part of the shelf. Several factors may have contributed to the
completion of the break, including a lack of sea ice to help resist,
or “push back,” against the stresses on the shelf ice in 2023.
The
second image, acquired with the Operational Land Imager (OLI) on
Landsat 8, shows the extent of Chasm 1 on January 12, 2021, about two
years prior to the break. Notice several other cracks across the
northeast part of the shelf. The “new crack” in that image
ultimately separated in February 2021 and formed Iceberg
A-74.
“The
rapid formation of subsequent rifts—to long-standing Chasm
1 and 2—and recent calving to the northeast makes it clear that
these shelf areas are dynamic with poorly understood stresses,”
said Christopher Shuman, a University of Maryland, Baltimore County,
glaciologist based at NASA’s Goddard Space Flight Center.
The
breaking (calving) of icebergs from ice shelves is part of a natural,
cyclical process of growth and decay at the limits of Earth’s ice
sheets. As glacial ice flows from land and spreads out over the sea,
shelf areas farthest from shore grow thinner. These areas are
stressed by storms and tides and thin as they are melted from above
or below, ultimately making them more prone to forming rifts and
breaking away.
As
for the “new” Brunt, it remains to be seen how the complex
floating glacial ice responds to the most recent calving event.
According to Shuman: “We have no solid idea what ‘normal’
really is for this unusual ice shelf.”
NASA
Earth Observatory images by Lauren Dauphin, using MODIS data from
NASA EOSDIS LANCE and GIBS/Worldview and Landsat data from the U.S.
Geological Survey. Story by Kathryn Hansen.
~~~~~~~~~~~~~~~~~
Other
large iceberg calvings
NASA Earth Observatory
Early
on July 12, 2017, satellites captured imagery of the new, massive
iceberg that broke away from Larsen C—an ice shelf on the east side
of the Antarctic Peninsula…..On July 13, the U.S. National Ice
Center issued a press release confirming the new iceberg and
officially naming it A-68.
February
22 - March 21, 2022
Collapse
of the ice shelf in
front of both the
Glenzer Glacier (C-37) and
Conger Glacier (C.38)commencing around 12 March 2022.