Antarctic Ice Discussion

[Gray-Wolf]

I see Ross Ice Shelf is in the news.

I get worried when I see a shelf the size of France making the news because we underestimated its basal melt rates( in it NW sector) by over 10 times its true losses!

In the noughties radar studies noted 'rucks' in the ice layers suggesting it grounded suddenly when it last formed. This would suggest fantastic back pressure from the ocean terminating glaciers behind.

As such there must be a 'break point' where enough contact with the ocean floor is lost as to allow it to surge forward and break its contact with the ground and so 'float off' on mass.

This would lead to a rapid, nay Larsen-esque, breakup of the shelf and the massive impact such would drove for the planet least of which would be the acceleration in the rate West Antarctica shed its ice via ocean terminating glaciers under gravity and Marine Ice Cliff Instability (M.I.C.I.)

Edited May 1, 2019 by Gray-Wolf

[Methuselah]

Antarctic instability is on the increase: https://www.bbc.co.uk/news/science-environment-48249287

[Kirkcaldy Weather]

https://www.google.com/amp/s/www.bbc.com/news/amp/science-environment-49885450

[knocker]

How Antarctica is melting from above and below

Upside-down rivers lapping at the bottoms of ice sheets and brilliant blue mini-lakes dotted on top may be speeding up Antarctic melting.

https://www.nationalgeographic.com/science/2019/10/how-antarctic-melting-above-below-ice-sheet/

[knocker]

 

[Mucka]

Have we really gone from record high Antarctic sea ice to record low Antarctic sea ice in just 5 years as NASA claim or has something changed in the way sea ice extent is recorded?

Edited October 31, 2019 by Mucka

[knocker]

3 hours ago, Mucka said:

Have we really gone from record high Antarctic sea ice to record low Antarctic sea ice in just 5 years as NASA claim or has something changed in the way sea ice extent is recorded?

that is correct. See the video I posted in the reports thread as it is touched upon there

[knocker]

Scientists head to Antarctica’s Thwaites Glacier

Nearly 100 scientists and support staff depart this week (13 November 2019) for the most ambitious mission to date for Thwaites Glacier in West Antarctica. In the second year of the International Thwaites Glacier Collaboration (ITGC), researchers from the United States (US) and United Kingdom (UK) will work in one of the most remote and inhospitable areas on Earth. It’s a five-year quest to understand the glacier and surrounding ocean system and its future contribution to global sea level.

Thwaites Glacier, covering 192,000 square kilometers (74,000 square miles)—an area the size of Great Britain—is particularly susceptible to climate and ocean changes. Over the past 30 years, the amount of ice flowing out of the region has nearly doubled. Computer models show that over the next several decades, the glacier may lose ice even more rapidly, as ice retreat progresses. Already, ice draining from Thwaites into the Amundsen Sea accounts for about four percent of global sea level rise. A collapse of the glacier would lead to a significant increase in sea levels of around 65cm (25 inches) over the coming centuries.

https://www.bas.ac.uk/media-post/scientists-head-to-antarcticas-thwaites-glacier/

[knocker]

New high-precision map of Antarctica’s bed topography

Quote

A team of glaciologists has unveiled the most accurate portrait yet of the contours of the land beneath Antarctica’s ice sheet – and, by doing so, has helped identify which regions of the continent are going to be more, or less, vulnerable to future climate warming.

https://www.bas.ac.uk/media-post/new-high-precision-map-of-antarcticas-bed-topography/

[knocker]

First look under Thwaites Glacier and Kamb Ice Stream

https://schmidt.eas.gatech.edu/2019-field/firstlookunderthwaitesglacier/

[Gray-Wolf]

New record for Antarctic continent reported

PUBLIC.WMO.INT

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The Argentine research base, Esperanza, on the northern tip of the Antarctic peninsula, set a new record temperature of 18.3°C on 6 February, beating the former...

 

[tablet]

On ‎07‎/‎02‎/‎2020 at 14:02, Gray-Wolf said:

New record for Antarctic continent reported

PUBLIC.WMO.INT

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The Argentine research base, Esperanza, on the northern tip of the Antarctic peninsula, set a new record temperature of 18.3°C on 6 February, beating the former...

 

Esperanza is 2000 miles away from the south pole , that would be the north pole equivalent to Oslo , which has an average summer temperature of 17.5°C (64°F) ,but  have been known to climb above 80 degrees Fahrenheit (27 degrees Celsius), as for the Esperanza temperature , a higher temperature of 19.8 Celsius ( 67.6 Fahrenheit) was recorded at Signy research station on January 30th 1982

if you look at the difference ( which is very easy using Ventusky.com  ) you will see the temperature difference between the peninsula and the main body of the continent , even in summer is vast .

 

[tablet]

but it is incredible what they are now finding at the south pole , very interesting read

https://www.nationalgeographic.com/news/2018/02/ross-ice-shelf-bore-antarctica-freezing/?fbclid=IwAR0LR0jOG4HmMc1VW_zATPYn9mRRgcMNBkvbh8-RMEKP8h1s6O0PKSLIDPs

 

[knocker]

Almost alien: Antarctic subglacial lakes are cold, dark and full of secrets

Quote

More than half of the planet's fresh water is in Antarctica. While most of it is frozen in the ice sheets, underneath the ice pools and streams of water flow into one another and into the Southern Ocean surrounding the continent. Understanding the movement of this water, and what is dissolved in it as solutes, reveals how carbon and nutrients from the land may support life in the coastal ocean.

https://www.sciencedaily.com/releases/2020/03/200304141410.htm

[Relativistic]

This thread seems to be dead! Thought I'd post an update on the situation in Antarctica.

According to NSIDC Antarctic sea-ice extent reached it's seasonal maximum on the 28th September, with 18.95 million km² the official figure. This ranks 11th highest in the satellite record. More info can be found here (you'll have to scroll to the bottom of the page):

https://nsidc.org/arcticseaicenews/

NASA have reported an extent of 17.7 million km² for the 4th November, approximately 200,000 km² above the mean for the satellite record, 600,000 km² below the date maximum set in 2013, and 1.2 million km² above the date minimum set in 2016. Area for the same date was 15.2 million km², approximately 400,000 km² above the mean, 700,000 km² below 2013, and 1.7 million km² above 2016. Overall, the current picture looks similar to the years 2010-2012. Data taken from this page (scroll to about halfway down):

https://earth.gsfc.nasa.gov/cryo/data/current-state-sea-ice-cover

 

Edited November 9, 2020 by Relativistic

[Relativistic]

Perhaps also of interest, the world's largest current iceberg, A68a, is on a collision course with South Georgia. This from the BBC:

"The world's biggest iceberg, known as A68a, is bearing down on the British Overseas Territory of South Georgia. The Antarctic ice giant is a similar size to the South Atlantic island, and there's a strong possibility the berg could now ground and anchor itself offshore of the wildlife haven. If that happens, it poses a grave threat to local penguins and seals. The animals' normal foraging routes could be blocked, preventing them from feeding their young properly. And it goes without saying that all creatures living on the seafloor would be crushed where A68a touched down - a disturbance that would take a very long time to reverse."

Full article here:

A68 iceberg on collision path with South Georgia

WWW.BBC.CO.UK

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If the world's biggest iceberg grounds at South Georgia island, it could devastate local wildlife.

 

Edited November 9, 2020 by Relativistic

[Relativistic]

The RAF have snapped some pictures of A68a from the air. The scale of this thing is astonishing.

World's biggest iceberg captured by RAF cameras

WWW.BBC.CO.UK

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A reconnaissance flight in the South Atlantic obtains spectacular imagery of the giant iceberg A68a.

 

[Relativistic]

Latest article on the monster that is A68a. Its edges seem to be rapidly breaking up but the sheer enormity of the thing means it's no less of a threat than it previously was to the ecosystem of South Georgia. It does, however, seem (roughly) to be moving with local currents; if it continues to do this and in the process manages not to wedge itself on the sea floor then it should drift harmlessly around South Georgia.

BBC News - Giant iceberg A68a prangs seabed and loses corner
https://www.bbc.co.uk/news/science-environment-55355381

Edited December 18, 2020 by Relativistic

[York-snow]

Just reading in the refreeze thread that Antarctic ice is at its highest for 50 years at this time of year. Is this down to an extensive period of favourable weather conditions or are there other factors helping? 

[BornFromTheVoid]

33 minutes ago, York-snow said:

Just reading in the refreeze thread that Antarctic ice is at its highest for 50 years at this time of year. Is this down to an extensive period of favourable weather conditions or are there other factors helping? 

Nah, it's not at it's highest. It saw it's faster growth in 50 years but is well below many recent years, such as the anomalous 2012 to 2014 period when sea ice coverage was breaking records.
The rapid growth came from winds blowing from the continent over the Ross and Amundsen Seas, creating large -ve temperature anomalies while also blowing the sea ice away from land causing rapid expansion.

Below is an animation I made at the time

 

 

[York-snow]

38 minutes ago, BornFromTheVoid said:

Nah, it's not at it's highest. It saw it's faster growth in 50 years but is well below many recent years, such as the anomalous 2012 to 2014 period when sea ice coverage was breaking records.
The rapid growth came from winds blowing from the continent over the Ross and Amundsen Seas, creating large -ve temperature anomalies while also blowing the sea ice away from land causing rapid expansion.

Below is an animation I made at the time

 

 

That makes more sense, thought it sounded too good to be true. Thanks for the explanation 

[BornFromTheVoid]

2 minutes ago, York-snow said:

That makes more sense, thought it sounded too good to be true. Thanks for the explanation 

Here's a link to a graph with Antarctic sea ice extent too, so it can be compared with other years. Just click on "Antarctica" under "Region Selector" on the right.

VISHOP

ADS.NIPR.AC.JP

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VIsualization Service of Horizontal scale Observations at Polar region

 

[knocker]

The fate of Antarctic ice shelves at 1.5C, 2C and 4C of warming

Antarctica’s ice shelves – the floating tongues of ice formed where the ice sheet meets the ocean – are especially useful indicators of a warming climate. Sandwiched between the atmosphere and ocean, they can be melted from above or below.

Recent decades have seen the collapse of two Antarctic ice shelves, while a third is even melting during winter.

Ice shelves perform a crucial role, holding back glaciers that would otherwise flow freely into the ocean, pushing global sea levels ever higher.

Our new study, published in Geophysical Research Letters, my co-author and I focus on how one half of the sandwich – the atmosphere – influences the stability of Antarctic ice shelves.

We run model simulations of surface melt and snowfall on Antarctic ice shelves under three levels of future warming about pre-industrial levels: 1.5C, 2C and 4C. 

The findings show that increasing quantities of meltwater on the surface of ice shelves can put them at risk of collapse through “hydrofracturing”. At 4C, for example, we find that four ice shelves – Larsen C, Wilkins, Pine Island and parts of the Shackleton ice shelf – are all vulnerable to collapse.

https://www.carbonbrief.org/guest-post-the-fate-of-antarctic-ice-shelves-at-1-5c-2c-and-4c-of-warming?utm_campaign=Carbon Brief Weekly Briefing&utm_content=20210409&utm_medium=email&utm_source=Revue newsletter

 

[knocker]

Identifying three ‘tipping points’ in Antarctica’s Pine Island glacier

Antarctica may seem far away for most of us, yet this remote continent contains enough ice to raise sea levels around the world by tens of metres. Its fate has important implications for coastal regions worldwide and the billions of people who live within them. 

Ice currently locked up in the Antarctic ice sheet flows to the coast within rivers of ice, known as ice streams or glaciers. These flow much more rapidly than the surrounding ice.

The acceleration and retreat of the many large glaciers that drain the Antarctic ice sheet is known as “dynamic ice loss”. It stubbornly remains the largest single source of uncertainty around projections of future sea level rise (pdf).

One cause for concern is that continued global warming may cause some glaciers to cross a “tipping point” known as the “marine ice sheet instability”. A tipping point is a threshold where a small, incremental change could push a system into a completely new state.

Being able to determine if and when a tipping point might be crossed is crucial for climate projections because the resultant change is effectively irreversible. Once crossed, even reducing greenhouse gas emissions back to pre-industrial levels may not be enough to recover what is lost. 

In a new study, published in the Cryosphere, my co-authors and I identify three distinct tipping points in model simulations of West Antarctica’s vast Pine Island glacier, which – if crossed – could lead to rapid and irreversible retreat. We also show that there are potential early warning indicators that signal when thresholds are approaching.

https://www.carbonbrief.org/guest-post-identifying-three-tipping-points-in-antarcticas-pine-island-glacier?utm_campaign=Carbon Brief Weekly Briefing&utm_content=20210409&utm_medium=email&utm_source=Revue newsletter

 

[Gray-Wolf]

Sea Level Rise Due to Antarctica's Ice Sheet Melting 30% More than Previously Estimated: Study | The Weather Channel - Articles from The Weather Channel | weather.com

WEATHER.COM

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Rising sea levels threaten island nations and coastal cities that harbour more than two billion people across the globe. - Articles from The Weather Channel | weather.com