"chasing ice"

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www.spiegel.de/wissenschaft/natur/eis-in-groenland-und-antarktis-schmelze-zum-anstieg-des-meeresspiegels-a-987106.html#js-article-comments-box-pager

www.climatecentral.org/news/waves-may-shrink-arctic-sea-ice-17898

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www.sciencemag.org/content/346/6214/1227

www.spiegel.de/wissenschaft/natur/antarktis-schelfeis-und-gletscher-schwinden-a-1006788.html


onlinelibrary.wiley.com/doi/10.1002/2014GL061940/abstract?campaign=%20wlytk-41855.5282060185



static2.egu.eu/media/filer_public/ac/f2/acf2d697-4a67-433b-bfd4-2a1f569cdb86/tc-2014-18.pdf



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www.deltares.nl/en/expertise/100795/climate-change

www.spiegel.de/wissenschaft/natur/klimawandel-bedroht-flussdeltas-und-damit-millionen-menschen-a-1006570.html


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www.the-cryosphere.net/9/103/2015/tc-9-103-2015.html

www.ibtimes.com/greenland-ice-melt-islands-vanishing-lakes-making-massive-ice-sheet-less-stable-study-1790300

www.spiegel.de/wissenschaft/natur/schmelzwasser-seen-schwaechen-groenlands-eisschild-a-1014251.html

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www.sciencemag.org/content/early/2015/03/25/science.aaa0940

www.spiegel.de/wissenschaft/natur/antarktis-packeis-seit-2003-deutlich-duenner-geworden-a-1025968.html

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www.waterencyclopedia.com/Ge-Hy/Global-Warming-and-Glaciers.html

www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2407.html

www.summitpost.org/the-disappearing-glaciers-of-glacier-national-park/550744

www.spiegel.de/wissenschaft/natur/kanada-70-prozent-gletscherschwund-bis-2100-a-1027303.html#ref=plista

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www.nasa.gov/content/sea-ice-off-east-antarcticas-princess-astrid-coast/

www.spiegel.de/wissenschaft/natur/satellitenbild-meereis-vor-antarktis-a-1028033.html

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en.wikipedia.org/wiki/Ross_Ice_Shelf

www.britannica.com/EBchecked/topic/510126/Ross-Ice-Shelf


www.zwallpix.com/ross-ice-shelf.html

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www.theguardian.com/environment/climate-consensus-97-per-cent/2015/may/11/ice-loss-in-west-antarctica-is-speeding-up

As I’ve previously noted, one of the most challenging problems in climate science deals with how to measure the Earth’s system. Whether ocean temperatures, atmospheric temperatures, sea level, ice extent or other characteristics, measurements have to be made with sufficient accuracy and geographical coverage so that we can calculate long-term trends. In some parts of the planet, the measurements are particularly daunting because of the ruggedness of the terrain and the hostility of the environment.

This brings us to a new study just published on Antarctic ice loss by Christopher Harig and Frederik Simons of Princeton. They work in the Princeton Polar Ice program. This study used satellite measurements to determine the rate of mass loss from this large ice sheet.

The ice sheet has two parts, a stable and large eastern part and a smaller and less stable western portion. The impact of climate change on these portions is different. The western part is losing mass at an increasing rate over the past years. In the east, however, the information is less clear. Increased precipitation (snowfall) is adding to the ice there, even while portions of the ice are warming.
Dr. Christopher Harig
Dr. Christopher Harig

The satellite method that these authors used actually measures the gravitational pull of the ice on two orbiting satellites. The huge ice sheet has such a large mass that it attracts objects toward it. As the ice melts and flows into the oceans, the attraction decreases – it is this change that is measured. The satellites are part of the Gravity Recovery and Climate Experiment (GRACE) project.

In the past, the satellites could only be used to make gross measurements over large areas. Their ability to separate what is happening in different regions is very limited. For such local measurements, other techniques had to be used.

The new paper provides an improvement to the resolution of GRACE. They find that the western part of Antarctica is losing mass at 121 billion tons (gigatons) a year. This rate has increased recently. In particular, in one region (the Amundsen Sea coast, the ice loss has doubled in the past six years). In the east, there is a small mass gain (approximately 30 gigatons a year). This mass gain partially offsets what is happening in the west but there is still a large loss of water to the sea each year.

I asked the lead author about this study and he told me,

It is very important that we continue long term monitoring of how mass changes in ice sheets. For West Antarctica in particular this is important because of how it is thought to be more unstable, where the feedbacks can cause more and more ice loss from the land over time. These strong regional accelerations that we see are very robustly measured and imply that Antarctica may become a major contributor to sea level rise in the near future. This increase in the mass loss rate, in ten years, accelerations like that show that things are beginning to change on human time scales.

The conclusions of the authors fits well with a study that I published with Ted Scambos late last year. In that paper, we discussed the ice loss from Antarctica. Our particular focus was on the rising ocean levels. What we showed by reviewing the literature was that as Antarctica’s mass decreases, changes to the gravity field will actually cause sea level rise to be greater than expected in the Northern Hemisphere.

This is important for people who are trying to make long term plans of coastal vulnerability and infrastructure. Again, we see that our changing climate will force us to adapt. Improving our predictions of what the future world will look like can provide guidance for efficient and effective adaptation.

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www.theguardian.com/environment/planet-oz/2015/may/05/melting-antarctic-failure-to-cut-emissions-now-could-raise-worlds-oceans-by-several-metres

Studies find West Antarctica’s ice sheet is melting faster. But a new look at the ancient past suggests it once pushed sea levels up by three metres

Graham Readfearn
@readfearn

Tuesday 5 May 2015 05.33 BST


Let’s start with an understatement. There’s quite a bit of ice in Antarctica and if enough of it melted it would make a real planetary mess.

About three million years ago so much of Antarctica melted that, according to some studies, all that extra water pushed the oceans about 17 metres higher than they are today.

So understanding Antarctica and its smaller polar opposite in Greenland has gigantonourmously big implications for the future.

These giants could reshape coastlines, swamp places currently occupied by hundreds of millions of people and make entire nations disappear.

Rising sea levels don’t just put places underwater, but every centimetre increases the impacts that storm surges have on people, homes and coastal infrastructure.

Waking the giants

In recent decades, Antarctica and Greenland have played minor roles in the world’s rising oceans. But this is changing.

Between 1993 and 2010, according to studies assessed by the Intergovernmental Panel on Climate Change, seas are rising by about 3.2mm a year – a rate that is accelerating.

About a third of that annual rise comes from the warming oceans (warmer ocean water takes up more space).

The second biggest driver is the melting of glaciers around the world (outside of Greenland and Antarctica).

The melting of ice sheets in Greenland and Antarctica only accounts for about one sixth of that 3.2mm, but as we already know these ice sheets are like sleeping giants.

Antarctic melting

Two studies last week looked at Antarctica and suggest the giant is probably already awake.

The first study (not that widely reported) was further confirmation that the melting of the West Antarctic ice sheet is accelerating (a study in May 2014 found the bits of the ice sheets attached to the land were on a “rapid retreat” and the following month another study reported satellite data showing an acceleration of the melt rate, now at 159 billion tonnes of ice per year).

The second study (not reported at all from what I can tell) tried to understand how Antarctica’s ice sheets behaved during the Pliocene – about three million years ago, when sea levels were likely about 20 metres higher than today.

The Pliocene is interesting because levels of carbon dioxide in the atmosphere were similar to today (400 parts per million in the atmosphere right now), with temperatures between 2C and 3C above where they were just before we kicked off the industrial revolution and started burning fossil fuels, loading the atmosphere with extra carbon dioxide.

The paper, published in the journal Earth and Planetary Science Letters, tried to work out how Antarctica’s ice sheets could have collapsed and how quickly it might have happened.

The scientists added two new processes to a computer model.

They modelled how big chunks of ice fall off cliffs into the ocean and also added a mechanism known as hydrofracturing (where melt water bleeds into small cracks in the ice, forcing open bigger cracks).

The results suggested that over the course of thousands of years Antarctica’s ice sheets were responsible for about 17m of sea level rise.

But what about West Antarctica – the area already showing signs of instability and potential collapse?

As the computer model ran, it took 100 years for the West Antarctic ice sheet to raise sea levels by about three metres.

The study also finds that the East Antarctic ice sheet (which is relatively stable right now compared to the West) would have contributed about 14 metres of sea level rise.

Lead author Dr David Pollard, of the Earth and Environmental Systems Institute at Penn State University, and co-author Professor Robert DeConto, of the University of Massachusetts, told me while it was “pretty clear” that their findings had implications for the future (to be explored in an upcoming paper by Pollard and DeConto) the study’s real focus was to better understand the past.

They said their paper was only a “preliminary exploration” and did not imply we’re in for three metres of sea level rise by the end of this century.

They also said there were large uncertainties in their work.

Fellow co-author Professor Richard Alley, also of Penn State University, explained:

The unfortunate reality is that this is a difficult system to model, which fairly clearly exhibits threshold behavior (or switching behavior… once a threshold is passed, the ice may switch to a new state rapidly with little chance of short-term reversal, and in West Antarctica, that will give a few meters of sea-level rise).

Such systems are typically quite difficult to predict—exactly how hard do you have to push to flip a switch?

I asked Alley about the implications from the study. He offered me an analogy.

A commuter expects traffic delays. The best possible trip has no traffic. The worst possible trip is being killed by a drunk driver or some similarly catastrophic outcome. What we expect… what is most likely… is on the “good” side of what is possible.

Many issues of climate change seem to have a similar distribution; we don’t see how raising CO2 greatly and rapidly will turn the world into the Garden of Eden, but we do see many ways that it might break things we depend upon.

As commuters, we spend a lot of money on air bags, antilock breaks, crumple zones, seat belts, child seats, traffic engineers, police, Mothers Against Drunk Driving, and other actions to minimize the dangers from events that we don’t expect to happen but that are possible. If the analogy is useful, it may have implications for wise actions.

This, I reckon, is a polite way of saying we should be cutting emissions of greenhouse gases to avoid slamming the only vehicle we have into a concrete wall.
Unstoppable?

Australian scientist Dr John Church is one of the world’s leading experts on sea level rise (he’s been studying it for a couple of decades) and was a co-ordinating lead author of the relevant chapter in the latest IPCC report.

That chapter found that without cuts to greenhouse gas emissions, sea levels could rise as high as one metre from where they were a decade ago. This could happen within 70 years.

Church told me the most recent studies on Antarctica did not, in his view, suggest the IPCC estimates were too conservative (while saying he was seen as being conservative among some sea level experts).

He said it was accepted that the Greenland ice sheet had “thresholds” that probably sat somewhere between 1C and 4C of global warming. Going over those thresholds would commit the world to rising sea levels for thousands of years. He added:

I would not dispute the idea that you could get substantially larger rises (beyond the end of this century) particularly with parts of West Antarctica being grounded below sea level and potentially unstable. I don’t think that three metres is out of the question.

Since the IPCC report, studies have shown that this process is now happening. We have triggered something that is potentially unstoppable.

Church said even though it was important to know how quickly sea levels would rise, it was also important to understand the fundamental impact our choices today could have on the planet’s future.

He said without “urgent mitigation” of greenhouse gas emissions “we commit the world to sea level rises for millennia”.

It is the decisions that we are making now that determine if we cross those thresholds.

In those IPCC projections, when you look at the last two decades of this century, the rate of sea level rise is up at one metre per century.

That is a rapid rise that can’t be turned around.

That’s a commitment we are making for future generations.

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www.forbes.com/sites/ericmack/2014/05/14/melting-antarctica-is-the-end-of-the-world-as-we-know-it-and-thats-a-good-thing/

www.spiegel.de/wissenschaft/natur/klima-der-antarktis-gletscher-im-suedwesten-schmelzen-a-1034994.html

www.spiegel.de/wissenschaft/natur/klima-5-ipcc-report-des-uno-klimarats-in-stockholm-2013-a-924789.html

www.spiegel.de/wissenschaft/natur/uno-klimareport-ipcc-verhandlungen-in-stockholm-schwierig-a-924728.html

www.spiegel.de/wissenschaft/natur/eis-in-groenland-und-antarktis-schmelze-zum-anstieg-des-meeresspiegels-a-987106.html

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www.ingentaconnect.com/content/igsoc/jog/pre-prints/content-ings_jog_15j017

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www.youtube.com/watch?v=gNb4SsIPJW4

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globalwarming.berrens.nl/globalwarming.htm

www.climatenewsnetwork.net/tag/ice-melt/

www.theguardian.com/environment/2015/aug/09/omg-nasa-project-oceans-melting-greenland

www.spiegel.de/wissenschaft/natur/alpen-rekordsommer-laesst-gletscher-schrumpfen-a-1053970.html

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www.washingtonpost.com/news/energy-environment/wp/2015/11/02/scientists-confirm-their-fears-about-west-antarctica-that-its-inherently-unstable/?tid=sm_fb