From the University of Southampton
A new study of satellite data from the last 19 years reveals that fresh water from melting glaciers has caused the sea-level around the coast of Antarctica to rise by 2cm more than the global average of 6cm.
Researchers at the University of Southampton detected the rapid rise in sea-level by studying satellite scans of a region that spans more than a million square kilometres.
The melting of the Antarctic ice sheet and the thinning of floating ice shelves has contributed an excess of around 350 gigatonnes of freshwater to the surrounding ocean. This has led to a reduction in the salinity of the surrounding oceans that has been corroborated by ship-based studies of the water.
“Freshwater is less dense than salt water and so in regions where an excess of freshwater has accumulated we expect a localised rise in sea level,” says Craig Rye, lead author of the paper that has been published in the journal Nature Geoscience.
In addition to satellite observations, the researchers also conducted computer simulations of the effect of melting glaciers on the Antarctic Ocean. The results of the simulation closely mirrored the real-world picture presented by the satellite data.
“The computer model supports our theory that the sea-level rise we see in our satellite data is almost entirely caused by freshening (a reduction in the salinity of the water) from the melting of the ice sheet and its fringing ice shelves,” says Craig.
“The interaction between air, sea and ice in these seas is central to the stability of the Antarctic Ice Sheet and global sea levels, as well as other environmental processes, such as the generation of Antarctic bottom water, which cools and ventilates much of the global ocean abyss.”
The research was carried out in close collaboration with researchers at the National Oceanography Centre and the British Antarctic Survey.
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The full paper Rapid sea-level rise along the Antarctic margins in response to increased glacial discharge is published in Nature Geoscience.
Rapid sea-level rise along the Antarctic margins in response to increased glacial discharge
Craig D. Rye, Alberto C. Naveira Garabato, Paul R. Holland, Michael P. Meredith, A. J. George Nurser, Chris W. Hughes, Andrew C. Coward & David J. Webb
- Nature Geoscience (2014) doi:10.1038/ngeo2230
The Antarctic shelf seas are a climatically and ecologically important region, and are at present receiving increasing amounts of freshwater from the melting of the Antarctic Ice Sheet and its fringing ice shelves1, 2, primarily around the Antarctic Peninsula and the Amudsen Sea. In response, the surface ocean salinity in this region has declined in past decades3, 4, 5, 6, 7, 8, 9. Here, we assess the effects of the freshwater input on regional sea level using satellite measurements of sea surface height (for months with no sea-ice cover) and a global ocean circulation model. We find that from 1992 to 2011, sea-level rise along the Antarctic coast is at least 2 ± 0.8 mm yr−1 greater than the regional mean for the Southern Ocean south of 50° S. On the basis of the model simulations, we conclude that this sea-level rise is almost entirely related to steric adjustment, rather than changes in local ocean mass, with a halosteric rise in the upper ocean and thermosteric contributions at depth. We estimate that an excess freshwater input of 430 ± 230 Gt yr−1 is required to explain the observed sea-level rise. We conclude that accelerating discharge from the Antarctic Ice Sheet has had a pronounced and widespread impact on the adjacent subpolar seas over the past two decades.
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Fortunately, they provide an SI file, seen here: http://www.nature.com/ngeo/journal/vaop/ncurrent/extref/ngeo2230-s1.pdf
Figure S4 is telling:
It seems there is a “pause” that has developed in SLR around Antarctica starting around 2005 continuing through 2012.
For reference, this map from NOAA/NESDIS shows that there is in fact about 2 cm of SLR around some parts of Antractica, but the main SLR is a big red patch in the Western Pacific:
While the Rye et al. paper says ice melt from the continent is the cause, it may also be simply a matter of winds. Note that the red spotch of SLR on the map above is mainly an issue of winds and ENSO. Around Antarctica, we have a strong circumpolar wind pattern, as is seen in the video below about ozone over Antarctica:
That circumpolar wind pattern around Antarctica can act as a sea level rise enhancer, as described in this paper:
Rapid subsurface warming and circulation changes of Antarctic coastal waters by poleward shifting winds
Spence et al. 2014
Abstract
The southern hemisphere westerly winds have been strengthening and shifting poleward since the 1950s. This wind trend is projected to persist under continued anthropogenic forcing, but the impact of the changing winds on Antarctic coastal heat distribution remains poorly understood. Here we show that a poleward wind shift at the latitudes of the Antarctic Peninsula can produce an intense warming of subsurface coastal waters that exceeds 2 °C at 200-700 m depth. The model simulated warming results from a rapid advective heat flux induced by weakened near-shore Ekman pumping, and is associated with weakened coastal currents. This analysis shows that anthropogenically induced wind changes can dramatically increase the temperature of ocean water at ice sheet grounding lines and at the base of floating ice shelves around Antarctica, with potentially significant ramifications for global sea level rise.
Bottom line: I’m not much worried about the claims made about SLR in Antarctica being due to ice melt. There may be some enhancement, but to say it is the sole reason, when other fcators are clearly at play is just your typical climate alarmism at work.
UPDATE: Having written this piece late in the evening, my fatigue must have caused me to forget this graphic. Temperature over Antarctica seems to to be ever so slightly negative trending.
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Let’s see ocean currents around Antarctica.
http://earth.nullschool.net/#current/ocean/surface/currents/orthographic=-16.18,-79.79,365
This is a fascinating post about the problems with defining ‘sea-level’ never mind the difficulties measuring to sub mm accuracy. Spend 3 minutes watching the video…
http://wattsupwiththat.com/2013/11/26/a-bunch-of-stuff-ill-bet-you-never-knew-about-sea-level/
From the video:
“The model has allowed geodesists themselves to correctly predict the average level of the ocean to within a meter everywhere on earth.”
So, are they saying it’s 3mm ± 1meter?
It’s in hoping the average lemming won’t catch that, and it appears there are many
That’s the only way that most climate scientism works… claimed measurements invert the normal measurement/tolerance relationship. Climateers almost always use value ranges that are at least two orders of magnitude smaller than the tolerance of the measurement. They fix this by having stastical models infill measurements until they create enough samples to pretend that they have statistically “increased” both accuracy and precision by three orders of magnitude. That means they can measure to +/-1mm with a sea level sensor who’s absolute accuracy is +/-1m. Isn’t climate science fun!
And the same problem reappears in the mapping of Greenland and the Antarctic also in the news today.Measurements accurate to a couple of meters are used to measure to the nearest few cm’s. And as pointed out on other blogs, if the completely erroneous results were correct, it would take many hundreds or thousands of years for the ice caps to ‘melt’ away. Total alarmist nonsense.
“Using radar techniques to map how water flows under ice sheets, UTIG researchers were able to estimate ice melting rates and thus identify significant sources of geothermal heat under Thwaites Glacier. They found these sources are distributed over a wider area and are much hotter than previously assumed.
The geothermal heat contributed significantly to melting of the underside of the glacier, and it might be a key factor in allowing the ice sheet to slide, affecting the ice sheet’s stability and its contribution to future sea level rise.
The cause of the variable distribution of heat beneath the glacier is thought to be the movement of magma and associated volcanic activity arising from the rifting of the Earth’s crust beneath the West Antarctic Ice Sheet.”
An example of a glacier in Iceland.
“There are about 30 known central volcanoes, or volcanic systems, in Iceland. Bárðarbunga, the second highest mountain of Iceland; ca 2000 meters above sea-level, is one of them. The volcano is placed in northwestern Vatnajökull ice cap and therefore covered with ice.
The enormous size and nature of Bárðarbunga was not fully recognized until it was observed in 1973 on an image from a satellite, 800 km above Earth (see below). A caldera in the volcano’s crown, 11 km long on the longer side, is covered with approximately 850 m thick glacial ice. Eruptions related to the central volcano can occur anywhere in the caldera, on the sides of the volcano and also in the fissure swarms to the NA and SW of the volcano, for a distance up to 100 km from the central volcano.
Inevitably, immense eruptions and explosive eruptions are a possibility in the system with imminent threat of ice melting in great magnitude causing a huge jökulhlaup (glacial outburst flood).”
Moderator… is this gibberish, internet slang or spam?
Thank you for the attention – please delete if inappropriate.
The username explains the content.
How can ice melt when its constantly way below zero C ?
The ice flows towards the coast and when it reaches warm (above freezing) water it melts, it also does get above freezing along the edge of the continent in the summer. So there is always some melting going on along the edges, more in the summer. There are also parts of the ice sheets floating on water that will occasionally break off and drift north and melt.
Subaerial melting is almost negligible in Antarctica even in summer. Mass-loss is due to calving, and to some extent to sublimation. However some melting occurs below sea-level since salt water will erode ice to some extent even when the water temperature is below zero (which is usually true in Antarctica). Most of the melting takes place well away from the Continent when the icebergs reach warmer waters.
Note that Iceberg B-9 which Chris Turney blamed for the “ship of fools” fiasco calved 1987 but which has remained close to Antarctica still hasn’t melted after 27 years.
It’s true. This year the water is higher on the sides of my kayak, especially on the same side when I tip slightly to get a better view of it.
If LOD is longer, SLR at the poles will increase, and slow at the equator, relative to each other. No melting required.
If LOD increases, SLR at the poles will increase and at the equator decrease relative to each other. No melting required.
After logging into wordpress to post the 5:37 comment, and refreshing this posting, no comment showed, so I re-entered it. Never saw this happen before.
As ever with a lot of the reports being released in the run up to Paris 2015, the words ‘straw’ and ‘clutching’ come to mind.
Breaking News…….
Russia opens new theme park in Antarctica…….film at 11
http://image.made-in-china.com/2f0j00KeNTPWQnZhku/Water-Slide-Hill-Side-WS-038-.jpg
A model confirms their predictions?
That’s the way it works. I saw a comment a few days ago that was priceless (I can’t remember who wrote it) and to paraphrase for this subject: “They’re using their models to train the measurements.”
Ah, well I don’t think the wind are dependent on AGW.
Would somebody please explain something to me? How is it possible that water in the Antarctic does not seek to normalize to the global sea level? I would think that sea level would be an indicator of planetary momentum and gravitational influences and continental land elevation changes. How is it that water in the Antarctic ignores these influences and puddles around the south pole? That it does not flow to the equator. Seems to me like a signal drift error or calibration fault, like the error we saw in the ice area satellite output? How does the water know it is in the Antarctic? What am I missing?
I’m waiting too.
Antarctica is surrounded by the recently-designated Southern Ocean. It is primarily delineated by the Antarctic Circumpolar Current which links the Atlantic, Pacific, and Indian Ocean basins. It is the largest ocean current, very fast.
The ACC is strong enough to bring about the recognition of the Southern Ocean as being something separate, and keeps the warmer ocean waters away from Antarctica. The isolation provided by the strong ACC would also allow for this piddly bit of SLR to stay around Antarctica without getting dispersed into those other warmer basins.
Side note, Our Changing Language: I was going to say piddlesome instead of piddly, meaning triflesome, but spell checker didn’t like it. Google thought I might have meant “meddlesome”, DuckDuckGo only returned results for meddlesome. But Google did find a few usages like with this Staffordshire U. animation student’s blog, showing the word is in use. How many other old words will the technology send to the memory hole in the pursuit of computerized uniformity?
Hello kadaka,
I read your response and thank-you. I am familiar with flow induced boundaries with elevation changes like standing waves at the outlet of the Columbia River on the west coat of the USA and the tidal bore that travels up the Bay of Fundy. The tidal bore in Canada is a transient event. The Coumbia River Standing wave is sustained by steady flow from the river.
If there is a blister of water atop the south pole, and a hydrodynamic bounday caused by the ACC, then there is an implication that there is huge melting to sustain the flow into the blister, if the event is not transient. But does not Pascals Law prevail? The water can migrate under the ACC?
Another question stimulated by your response: Could a change in the ACC account for a change in the boundary effects, sufficient to sustain a 2 cm blister?
kadaka (KD Knoebel)
September 1, 2014 at 10:16 am
… How many other old words will the technology send to the memory hole in the pursuit of computerized uniformity?
As many as we allow it to. So, oppose the trend. Use the word and let those who don’t know it use a dictionary – a good one, not an on-line version.
An interesting pause in the time-series. However, comparisons of a regional to global have to be on a same-area basis. Furthermore, there are no accounting of the self-gravitational potential of the regional to the global. Therefore, this paper is failed.
The warmists tried ignoring the Antarctic while focusing on the Arctic. Since they are a distracted lot, they had to address the Antarctic ice records with pecking at it with weak studies. In their methods, quantity replaces quality and outcomes so this is considered plugging the (ice) dike.
350 GT = 350 km3 excess water, so a good deal less than the volume of the smallest Great Lake, Lake Erie, at 480 km3? Only it’s distributed around a continent? Is that significant at all?
What part of winds displace water, do these experts not understand?
Any boat owner on freshwater lakes knows this.
I lean toward a Guam Moment, the additional ice must be causing the continent of Antarctica to tip.
Now that the dishonesty of Team CAGW ™ IPCC is an open secret, Climatology is getting stale.
However I remain entertained and amused by the speed of the Glibbering Climb Down.
Seems to be an exponential decay, but there is no hiding the decline in the quality of true believer, I miss their absolute certainty, holier than thou personas and find the current snivelling does nothing to engender any sympathy from me.
The references cited by the authors are flawed and failed as well.
Dynamic topography of the souther ocean is very strong and failure to account (ignore) it is a reason to fail this paper.
maybe all the additional ice is weighing down the continent, hence the apparent sea level increase?
(this comment made half in jest, but it’s at least as coherent as some of the other offerings here. %-)
For the record, Mt. Erebus, located on Ross Island, erupted as recently as 2011, spewing ash. Also, Erebus contains one of the four permanent molten-lava pools on earth. Are we factoring this into our understanding?
Can I ask some newbish amateur questions? Maybe someone will tackle a few of these for me. If so, much obliged.
(1) if there is increasing sea ice at the Antarctica, won’t that have the effect of raising local sea levels, like dropping ice cubes in a glass? I mean if the ice increases are due to freezing seas, maybe not. But if they are due to increased atmospheric moisture coming into the region, such as from snow, wouldn’t that raise local seas?
(2) I realize global warming predicts melting ice sheets at the poles. But it seems to me that a warming world would increase ice at the poles, unless the temperatures rose enough where it was above freezing. It seems to me that a warming world will have more moisture in the air. Moisture which will fall as snow in Antarctica, thereby growing the ice sheets.
(3) if there has been a 17 year pause in warming, why would the Antarctic ice sheets be melting?
(4) I once read about the complications involved with analyzing sea levels. Continents are moving, sinking, rising. And land is sinking or rising depending on local conditions. The land is rising in many places as it has been since the end of the last ice age when ice pressed the land in. Measuring sea levels seems so complicated and involves so many elaborate considerations and algorithms that only the people making that it requires one to place an inordinate level of trust in the people designing those measurements. Is there any reason I should trust the objectivity of these handful of scientists doing the studies? Are there honest peers checking and duplicating their methods? It seems to me measuring minute levels of sea level rise over a small period of time must have a margin of error that is larger than the claimed increase. And I fear that the value of the bias which is built into these studies is larger than the small increments of sea rise being claimed.
Thanks!
“The computer model supports our theory…”
Oh shut up.
I’ll bet their claims of increased salinity and added fresh water are about as reliable as their model. Not so much.
Later we’ll find out they never really measured either. That they had made presumptions and theorized (ginned up) the increases.
“Freshwater is less dense than salt water and so in regions where an excess of freshwater has accumulated we expect a localised rise in sea level,”
Ouch. If the Antarctic ice extent has been increasing during the period studied, then the summer melts put more fresh water in the local region around the Antarctic and so their figure S5 “Regional anomaly in summer (January to April) linear sea level trend, 620 1992-2011, relative to the global barystatic rate of sea level rise” might be explained by this seasonal influx of fresh water.
I wonder if they’ve stuck their fingers into the water and sucked them to check the salinity [there may be more sophisticated measurement methods available these days].
If the “sea level increase” is due to an influx of fresh water there should be a thin surface layer of water of relatively lower salinity even with mixing etc.
Or did they just model it ?