Boaty McBoatface & friends to explore Thwaites glacier

[TheVat]

https://apnews.com/article/science-glaciers-antarctica-e9687077d7295e8218ba7cbcb9246ca3

 

A team of scientists is sailing to “the place in the world that’s the hardest to get to” so they can better figure out how much and how fast seas will rise because of global warming eating away at Antarctica’s ice.

Thirty-two scientists on Thursday are starting a more than two-month mission aboard an American research ship to investigate the crucial area where the massive but melting Thwaites glacier faces the Amundsen Sea and may eventually lose large amounts of ice because of warm water. The Florida-sized glacier has gotten the nickname the “doomsday glacier” because of how much ice it has and how much seas could rise if it all melts — more than two feet (65 centimeters) over hundreds of years.

[mistermack]

"Satellite measurements by NASA indicate a still increasing sheet thickness above the continent, outweighing the losses at the edge."^[

Wikipedia. 

[TheVat]

Could you cite the specific wiki article?  I would like to get some context for that, as well as the primary source they used.  Also, why do you think the scientific community is largely in agreement that there is measurable net ice loss there?  (I seriously hope this not some Heartland Institute (Koch Brothers front org.) factoid that's been allowed into Wikipedia!)

[mistermack]

I hope this link works. Otherwise, just search Antarctic Ice Sheet. 

https://en.wikipedia.org/wiki/Antarctic_ice_sheet#:~:text=Satellite measurements by NASA indicate a still increasing sheet thickness above the continent%2C outweighing the losses at the edge.[4]   

[Doogles31731]

Just to ease TheVat’s concerns, the Wikipedia article on the subject cites a 2015 NASA report -- NASA (2015; https://www.nasa.gov/feature/goddard/nasa-study-mass-gains-of-antarctic-ice-sheet-greater-than-losses) in NASA Study: Mass Gains of Antarctic Ice Sheet Greater than Losses

An excerpt of the Introduction states “A new NASA study says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.

The research challenges the conclusions of other studies, including the Intergovernmental Panel on Climate Change’s (IPCC) 2013 report, which says that Antarctica is overall losing land ice.”

The report goes on to say that that the original paper was published in the Journal of Glaciology, and it cites many comments made by the lead author Jay Zally.

[mistermack]

The situation in the Arctic is not so bad currently either. Although it may be temporary, the sea ice has bounced back to the 2010 mean level. Although the overall trend might still be downwards, it's not in line with the doomsday forecasts that I've been reading for the last forty years. I can remember climate scientists predicting an ice-free north pole, by the turn of the millenium. And anybody who queried it got jumped on as a denier. 

This is the arctic ice extent today : 

Admittedly it will look worse next september at the end of summer, but it's still nothing like the disaster that's been constantly foretold.

[TheVat]

However, reading further in the wiki article (thanks, Mac) suggests that overall Antarctica ice is decreasing due to net loss in the west end...

From the wiki:

If the transfer of the ice from the land to the sea is balanced by snow falling back on the land then there will be no net contribution to global sea levels. The general trend shows that a warming climate in the southern hemisphere would transport more moisture to Antarctica, causing the interior ice sheets to grow, while calving events along the coast will increase, causing these areas to shrink. A 2006 paper derived from satellite data, measuring changes in the gravity of the ice mass, suggests that the total amount of ice in Antarctica has begun decreasing in the past few years.^[19] A 2008 study compared the ice leaving the ice sheet, by measuring the ice velocity and thickness along the coast, to the amount of snow accumulation over the continent. This found that the East Antarctic Ice Sheet was in balance but the West Antarctic Ice Sheet was losing mass. 

 

(end quote)

Also note a further contextual factor - calving at the edges increases the total of lower albedo oceanic surface which can absorb more insolation.  Ice reflects, sea absorbs.  That is the big feedback potential that climatologists talk about a lot.

2 hours ago, mistermack said:

The situation in the Arctic is not so bad currently either. Although it may be temporary, the sea ice has bounced back to the 2010 mean level. Although the overall trend might still be downwards, it's not in line with the doomsday forecasts that I've been reading for the last forty years. I can remember climate scientists predicting an ice-free north pole, by the turn of the millenium. 

 

Just to keep things up to forum standards, could we have a citation for those ice free predictions?  Were they widely peer reviewed and agreed upon?  Or were those modeling approaches being revised at that time and much debated?  For sure, climatology in its infancy had to try and reject many models.  

Also the extensive permafrost melts in the past decade may point to an Arctic situation that is fairly serious, given the feedback effects as ancient former marshlands and bogs thaw and release both methane and various particulates.  And Arctic ice is shrinking, and any shrinkage opens up the lowered albedo feedback system as well.  

 

This is a good summary on the decline of Arctic ice pack...

https://en.wikipedia.org/wiki/Arctic_sea_ice_decline

 

 

[Doogles31731]

The Arctic situation appears to be quite different from that of the Antarctic. In response to TheVat's request, I took it upon myself to check the IPCC position on the Antarctic in 2013 wrt sea level rises -- ""Just to keep things up to forum standards, could we have a citation for those ice free predictions?  Were they widely peer reviewed and agreed upon?  Or were those modeling approaches being revised at that time and much debated?" 

In the 2013 IPCC report, Section 13.4.4.1 (https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter13_FINAL.pdf), the opening paragraph states “Because the ice loss from Antarctica due to surface melt and runoff is about 1% of the total mass gain from snowfall, most ice loss occurs through solid ice discharge into the ocean. In the 21st century, ablation is projected to remain small on the Antarctic ice sheet because low surface temperatures inhibit surface melting, except near the coast and on the Antarctic Peninsula, and meltwater and rain continue to freeze in the snowpack (Ligtenberg et al., 2013). Projections of Antarctic SMB changes over the 21st century thus indicate a negative contribution to sea level because of the projected widespread increase in snowfall associated with warming air temperatures (Krinner et al., 2007; Uotila et al., 2007; Bracegirdle et al., 2008). ... ”

On closer scrutiny, the IPCC did not in fact claim that the Antarctic melt was contributing to a sea level rise. Zally et al’s 2015 paper really affirmed rather than contradicted what the IPCC had actually stated.

This implies of course that the Antarctic as a whole is NOT contributing to sea level rises.

At least that's my interpretation of the Report. I hope I haven't misinterpreted the above.

The trip to  the Antarctic, as mentioned in the OP, will no doubt contribute to our knowledge about peripheral ice adding to sea levels, but one would hope that they would mention in their report that the evidence suggests that this peripheral ice breakaway is offset by snowfalls inland. 

 

[mistermack]

6 hours ago, TheVat said:

could we have a citation for those ice free predictions?

Afraid not, that's why I just said "I remember" to make it clear. I wasn't collecting references 25 years ago, or buying peer reviewed journals. But if you remember the turn of the millenium differently, that's fair enough. From what I remember, you didn't need a peer reviewed paper to get on tv or in the papers at the time. It was a time of anything goes, and little criticism. 

This is the site I use for facts about ice :  http://nsidc.org/arcticseaicenews/   

Their long term graphs show little change over the last fifteen years, averaged out, although it's still possible to make the case for a continued downward trend in the Arctic ice. If you take the last fifteen years in isolation, the trend looks pretty flat, but if you add on the previous fifteen years, it looks like an ongoing drop. 

[Doogles31731]

My apologies. I thought TheVat was questioning the authenticity of the NASA statement that Zally et al's paper was contradicting the IPCC 2013 Report on the Antarctic. He was in fact questioning mistermack's statement that "Although the overall trend might still be downwards (sea ice in the Arctic), it's not in line with the doomsday forecasts that I've been reading for the last forty years."  I believe TheVat was correct in implying that no scientific journal appeared to have made any predictions for an early disappearance of sea ice in the Arctic. Popular science stories may have been different, but they are difficult to check.

While doing a scientific literature check, I did find a 2000 article in Science Progress that was titled Arctic sea ice and climate change—Will the ice disappear in this century? and predicted that “sea ice could disappear in the Arctic this century, at least in the summer.” -- https://www.jstor.org/stable/43424174. I'm sure they meant 'by the end of 2100'. This seems possible to my mind and it gives us plenty of time to adapt.

I mentioned this because, technically, any article published in the year 2000 was still in the 20th century. The 20th century did not end until the END of the year 2000. The whole world celebrated the end of the 20th century at the start, instead of the end, of the year 2000. 

[Ken Fabian]

On the other hand (and more recently) NASA also says, contradicting https://www.nasa.gov/feature/goddard/nasa-study-mass-gains-of-antarctic-ice-sheet-greater-than-losses  - from Grace Satellite gravimetric data -

Quote

- between 2002 and 2020, Antarctica shed approximately 150 gigatons of ice per year, causing global sea level to rise by 0.4 millimeters per year.

And -

Quote

Areas in East Antarctica experienced modest amounts of mass gain due to increased snow accumulation. However, this gain is more than offset by significant ice mass loss on the West Antarctic Ice Sheet (dark red) over the 19-year period.

I am not sure how the different data is reconciled. I would note that data based on ice and snow surface elevations have innate potential to be misleading about mass changes - I'm inclined to think the gravimetric data has less room to mislead.

Edited January 9, 2022 by Ken Fabian

[Doogles31731]

That reference you cited, Ken Fabian, is the one that I cited a few posts back. It was the NASA Report about Zwally et al's research in which NASA incorrectly claimed that it contradicted the IPCC 2013 Report. It had in fact confirmed Section 13..4.4.1 of the 2013 IPCC Report.