AlleyCat
2024-04-16 12:26:15 UTC
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PermalinkMore evidence emerges that Antarctica has undergone rapid glacier and sea ice
expansion in recent centuries, in line with the long-term and recent Antarctic
cooling trend. [emphasis, links added]
West Antarctica's mean annual surface temperatures cooled by more than -1.8°C
(-0.93°C per decade) from 1999-2018 (Zhang et al., 2023).
Not just West Antarctica, but most of the continent also has cooled by more
than 1°C in the 21st century. See, for example, the ~1°C per decade cooling
trend for East Antarctica (2000 to 2018) shown in Fig. ES1 (right).
Image Source: Zhang et al., 2023
According to a new study, about 6,000 years ago Antarctica's Collins Glacier's
frontline was a full 1 km southwest of its current extent. The frontline
advanced to today's extent ~5,000 years ago.
"Previous studies proposed that 6,000?yr BP [Before The Present Era], the
frontline position of the Collins Glacier was located 1?km further southwest
than the present and that the current frontline was first attained at
approximately 5,000?yr BP."
The glacier then continuously retreated south of the modern extent for another
4,000 years, with peak ice loss 1,000 years ago (as shown in the 1,000-year
"Proglacial lake environment" image).
In the last 1,000 years, this glacier has rapidly re-advanced back to the
glaciated extent from 5,000 years ago, which is in line with the sustained
cooling trend ongoing since the Medieval Warm Period.
Image Source: Piccini et al., 2024
Throughout the Holocene (Medieval Warm Period, Roman Warm Period, and earlier)
and until a few hundred years ago (from ~7,100 to 500 years before the
present), coastal Antarctica's Victoria Land (VLC) was substantially warmer
than today.
The Ross Sea was also sufficiently ice-free to allow for elephant seal
populations (as large as ~200,000 individuals) to thrive at 73-78°S.
Today, however, elephant seal populations - which require extended sea ice-free
sea waters to breed, forage, and provide nourishment for their pups - can no
longer subsist anywhere even remotely close to the coasts of the Antarctic
continent. It is now too cold and the sea ice is too extensive.
The substantially reduced number of remaining elephant seals existing today can
only survive on subantarctic islands (South Georgia, Macquarie) at southern
South American latitudes (~54.5°S) situated 2,400 kilometers north of VLC (Koch
et al., 2019).
The "genetically distinct" VLC elephant seal populations that endured
throughout the Holocene and even through Medieval times have tragically died
off in the last few centuries due to the modern-era cooling gradient and
subsequent ice cover expansion (Hall et al., 2023).
"Across all sites, there is a precipitous drop in the number and geographic
extent of the SES [southern elephant seals] remains within the last millennium"
"...the documented population crash and abandonment of the entire coast by SES
after ~1000-500 yr BP was due to return of heavy sea ice"
Image Source: Hall et al., 2023
And with the modern sea surface temperatures cooling and southern hemisphere
sea ice expansion in recent decades, even the subantarctic islands in the South
Pacific that SES are limited to occupying today may not be sufficiently warm
and ice-free to accommodate remaining populations.
Today's southern elephant seals are thus ironically threatened by cooling in
the era of anthropogenic global warming.
"[P]ack-ice expansion (both duration and extent) in the Ross Sea over the last
several decades has been linked to reduced female foraging in this region,
consequent low weaning weights and survival of pups, and ultimately the decline
of the Macquarie Island population."
Interestingly, Hall et al. also report that not only have the last few
centuries (including the present) been "the coldest, iciest conditions in the
post-glacial period" (see the blue sea ice and red temperature trend lines on
the Holocene timeline), but even the last glacial period had periods (~50,000
to 25,000 years ago) with less sea ice than today, allowing SES to occupy the
VLC coast.
=====
April:
Another Three Avalanche Deaths In The Alps
Indian State Suffers Coldest April Day On Record
The Arctic Was Warmer In The 1920s
Today's Arctic Sea Ice Extent Matches 1996
Snow Remains In Northern India
Germany Regrets Disbanding Nuclear Plants, It Was A "Mistake"
Yukon Snowpack Breaks Records
Early Snows Hit Australia's Ski Fields
It's Still Snowing On Kilimanjaro... Al Gore Was Wrong (as usual)
Alyeska Exceeds 700 Inches
Rare April Snow Hits Boise
Montreal's Snowiest April Since 2010
Clearing Crews Reach Baralacha
Antarctica At -75.8C (-104.4F)
Alta Posts Rare Back-To-Back 600+ Inch Winters
Indian Army Rescues 80 Trapped By Spring Snowfall
Remarkable Antarctic Sea Ice Recovery
April Nor'Easter Drops Feet Of Snow
600,000 Lose Power As 'Spring' Storm Batters Quebec
Avalanche Hits Helicopter In The Alps, Killing 3
Scandinavia Breaks Historic Low Temperature Stretch
New Zealand's Record-Cold March
Rare April Snow To Dust Bay Area Peaks
More Snow For The Midwest/Northeast
Scandinavia Extends Spell Of Historic April Cold, As Europe's Mountain Snow
Breaks Records
Sweden Sets Coldest April Temperature
Swiss Avalanche Kills 3
Utah Snowpack At 132%, California Defies The 'Experts'
Anchorage Only 6.3" Away From All-Time Record
Colder-Than-Average March At Vostok
Antarctica Dips Below -100F
"Significant Spring Snowstorm" Takes Aim At Canada/Northern US
April Snow Builds Across Europe's Higher Elevations
