Why do Science in Antarctica?

Nature, in the course of editorialising on the vast waste of money that is the US return to the moon plan (although they don't say that), sez, making the analogy with the return to the South Pole in the IGY:

since humanity's return to the South Pole, Antarctic science has been central to the great project of understanding the changes that humans are inflicting on the Earth. An Antarctic component to the nascent global carbon dioxide monitoring effort was established in 1957. Since then the contributions have been legion: discovery of the Antarctic ozone hole; the extraction of greenhouse-gas records and climate data reaching back more than half-a-million years from ice cores; the study of the anomalous warming of the Antarctic peninsula; and so on.

Which is a nice set of research results, but not very good if you're defending science *at the pole*, ie Amundsen-Scott station. CO2 is done as A-S, but could (I presume) be done more easily at McMurdo. Ozone hole was us, of course :-). Deep ice cores aren't done at the pole (its not a very good site for coring). Peninsula is exciting but, obviously, not done at the pole. Maybe there is a lot of "and so on" science too.

[Update: as several people point out (I thought of this too) its also good for astronomy. But Nature forgot that :-) ]


More like this

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The pole is a lot higher than McMurdo which has advantages for CO2. OTOH, I have seriously considered overwintering at McMurdo after I retire from my day job, but the pole, no way.

Well, you're being a little unfair to Nature. They didn't say "since humanity's return to the Antarctic, South Pole science has been central..."

By Steve Bloom (not verified) on 05 Feb 2007 #permalink

Of course the real reason for "doing science" in Antarctica is to maintain a strategically important foothold on that continent, as any fule kno.

The greater question is why to employ computer modellers who have never set foot there :-)

There's some marginally interesting stuff going on in the snow that was first measured at South Pole. There's NOx coming straight out of the snowpack as a result of the photolysis of nitrate ions. This NOx gets involved in photochemistry to produce ozone well above what you'd predict otherwise. It's of more interest for atmospheric chemists because it's entirely restricted to the boundary layer though. There was some talk at the beginning that this could have climatic implications, but I'm not sure what effect a 100 metres blanket of enhanced ozone will have on the radiative balance. It is found across the whole plateau, so who knows.

Curious -- I read this:
" ...The research team found that the Recovery stream accelerates significantly as it passes over the lakes.

"Upstream of the lakes, it flows at two to three metres per year; after passing them, at about 50 metres per year.

"Whether there is a link to climate change is another question. The lakes lie in the eastern portion of Antarctica, where evidence suggests the icecap may be gaining mass rather than losing it.
"As this research team puts it: 'The Recovery sub-glacial lakes and the associated Recovery ice stream tributaries have the potential greatly to affect the drainage of the East Antarctic ice sheet, and its influence on sea level rise in the near future.'"

and read the abstract for this:

"Rapid Sediment Erosion and Drumlin Formation Observed Beneath a Fast-Flowing Antarctic Ice Stream - AM Smith, T Murray, KW Nicholls, K Makinson, G ... - American Geophysical Union, Fall Meeting 2005

Couple questions: at the bottom of the icecap (everywhere, I think) there's enough ice thickness that it's grounded. How close are any areas of the ice to neutral? I realise the water pressure at the bottom of the ice is ---- whatever it is, at a mile or two below sea level.

[There are bits of W Antarctica that are fairly close to neutral - part of its possible instability -W]

Does water under pressure carry more silt than water at 1 atmosphere pressure?
I ask because the rapid drumlin article says, yes, they looked through the ice and saw one form, really fast -- these had been thought to be slow creatures.

But -- given that liquid water is flowing along the interface between ice and ground, whatever that ground is (presumably rock) --- how much of what kind of rock flour can that stream carry?

I know it's possible to "fill up" a moving stream's capacity to carry a load -- any time the flow becomes turbulent it drops some and then when it gets laminar it can and will pick up more again. It's one of the conundrums of restoration: if I take a nasty eroding stretch of stream and methodically make check dams and secure eroding banks and plant willow, and otherwise do everything I can to make that stretch of streambed turbulate the flow and be dropping rather than carrying all the sediment it can.

Anytime you turbulate a flow, whatever's flowing drops some of what it's carrying.

If there's a dead air spot on the interface, anyplace a vortex or ripple consistently leaves undisturbed, whatever silt (for a stream), leaves and dust and seeds (for a breeze), or household lint (for a fan).

So --- we're at the bottom of a glacial ice cap. There's a lot of melting way above but we're two miles down and it's been dark and quiet for a while. But every now and then the ice does flow far enough to cause the contact plane to shift downstream a bit.

There will be some flow, where there's excess heat or friction or impurities in the water if anything can change its melting point in those conditions.

We get flows of water; some of them are carrying silt.

That passes through a space where there's a bit of a void, the stream spreads out and slows down and drops what it's carrying.

So, finally, a question -- isn't a drumlin seen happening so fast, likely to be built up by silt filling a void that's melted a bit, on the bottom of the ice, and so going to get silted up as fast as the flowing water going by can provide the silt?

How else could they be happening, under the ice and so fast? And doesn't this lead to some ideas about streamflow rate?

And, has anyone had a look at the Channeled Scablands recently? They were an icecap letting go --- are we sure the water was on top of or behind that ice, or could it have been building up underneath the ice like this?

Because there's one other thing a very silty fast strong flow will do going downhill --- cut away what's in front of it and just rearrange it if it's so full of silt it can't keep any more suspended. A topside melt lake will be mostly water; an under-ice-cap flow must be quite a bit of silt.

Done handwaving; I'll go catch up on the drumlin stories. Turns out they're seen on Mars, resembling those in the Scablands. Hmmmm.

[Ah, I know nothing of drumlins - sorry -W]

By Hank Roberts (not verified) on 23 Feb 2007 #permalink

Well, drumlins were thought to be long slow streamflow processes, til that snapshot of fast formation under the ice. Perhaps nobody knows yet. Got grad students? (grin)

Does this make sense?
"... Martin Siegert, a glaciologist at the University of Bristol in England. "\...

The melting point of ice in environments such as Lake Vostok is related to the thickness of the ice above the water. The melting point is colder under thicker ice, as it is at the northern end of the lake.

The water that melts at the northern end will thus be colder and less dense than water at the southern end. "The density contrast between these waters will cause the circulation," said Siegert.
I wonder why the melting point would be colder under thicker ice, and if that relationship is linear, or describes only the Lake Vostok depth conditions.
(Clipped from a BBC story, lost the cite, sorry).

[Because of the pressure effect. Pressure will melt ice, you know that; ie the melt point gets lower under pressure -W]

Here's another source for the "20 feet in 100 years" sea level rise possibility:

" ... the WAIS is considered unstable because a large portion of it floats on water above the sea floor. For this reason, scientists suspect that the WAIS is particularly sensitive to global climate change, and they have long debated whether global warming would cause the WAIS to collapse. ...

"If so much ice melted into the oceans at once, sea levels could rise as high as 20 feet all over the world, within a single century. ..."

[Ermm, OK, but its still *if* -W]


I'd speculate the whole idea of meltwater lakes sitting on top of icecaps and spilling over is due for a revision --- and that we'll be looking at things like drumlins completely differently now that we know they can form rapidly under ice. It still has to be happening from deposition by flowing water --- but it's not surface water.

Looking at the radar maps of the ground under the ice, what I see is the major areas below sea level looking like places not pushed down dramatically by the overlying ice, but like river drainage channels. As the ice accumulated and moved, now that we know about under ice flows, the icecap would push whatever rock flour and warm-epoch silt out toward the edges, carrying it along with meltwater.

What do you see looking at the radar maps? Looks to me like --- clear shapes toward the middle; less and less clear out to the edges along each likely river course, and big smooth rounded banks of what I'd expect to be extruded silt/rock flour along the edges.

I think under the ice caps water is flowing 'uphill' from the basins around the center, radially, and as it spreads out it flows slower, so the farther it goes toward the circumference the more silt it drops.

Fill a deep bowl with peanut butter, put a shallower bowl on the top, push down ....

Okay, enough speculation from the uninformed and uneducated moi. Just wondering.

By Hank Roberts (not verified) on 24 Feb 2007 #permalink

Belatedly, I find New Scientist covered all these ideas (except they haven't quoted anyone anticipating my Channeled Scablands speculation, you read that first here) in their special December 2-8, 2006, special issue: "Hidden World Beneath Antarctica's Ice."

It's really quite good. Other than being quietly overwhelming.

"Water moves in mysterious ways. The weight of the ice squeezing downwards counts for much more than local hills and valleys in telling water where to go. 'You can have lakes sloping down the sides of mountains, you can have uphill waterfalls, it's wacky' [Don Blankenship, geophysicist at U. Texas] ....Blankenship fears that warming since the end of the last ice age has melted the base of the ice, and this may already be priming some parts of the ice sheet to slip. East Antarctica could be ready to open its floodgates.

"David Marchant from Boston University believes this may have happened before. .... one place in particular, a tortured landscape of channels and pits known as the Labyrinth .... sinuous .... often potholes .... channels that stop abruptly .... what you'd expect if they had been made by water that then flowed off down a different path, ... or plunged [that's in an upward direction --hr] into the overlying ice.

"He became convinced that the Labyrinth had been carved by a massive under-ice flood, and he published his ideas in July (Geology, v34, p. 513). .... potholes that are 200 metres across and 50 metres deep,' says Marchant. 'They are just enormous features. They're the largest potholes in the world. The water quickly stripped away all sedimentary rocks, and then lifted blocks of granite bedrock more than 2 metres wide ..."

Okay, I think this is serious stuff. Anyone found any more about it?

By Hank Roberts (not verified) on 28 Feb 2007 #permalink

Ok, it's been covered. Good references, including the Antarctic

"... By about 1990 the way that glaciologists envisaged
basal water flow had greatly changed, largely owing to
the realization that R channels could not form the basis
for an explanation of observations from surging Varie-
gated Glacier [Kamb et al., 1985] and rapidly moving ice
stream B in Antarctica [Blankenship et al., 1987]. Theo-
ries were developed to elucidate the hydraulics of water
flow through linked cavities [Walder, 1986; Kamb, 1987],
deformable till [Alley et al., 1987], and till-floored chan-
nels [Walder and Fowler, 1994]....

To summarize, the drainage system under any given
glacier comprises several or all of the morphologically
distinct components described in this section. A slow,
nonarborescent drainage system, comprising a mixture
of elements including cavities, permeable till, and
conduits incised into the bed (i.e., Nye channels and canals),
probably covers most of the glacier bed and is nearly
fixed relative to the bed. The water pressure in the slow
drainage system is commonly close to the ice-overburden pressure.


By Hank Roberts (not verified) on 01 Mar 2007 #permalink

Say what? Has this story showed up as science yet?

------ begin snippet -----

... early conclusions drawn by geologists at Andrill (Antarctic Geological Drilling), the multinational consortium leading the project, which recently released preliminary data from the drilling on its Web site. ...

A first look at conditions that prevailed five million years ago

"This time we were able to drill into layers representing the period between five and 12 million years ago," Andrill team member and geologist Lothar Viereck-Götte told SPIEGEL ONLINE. What these unique ice cores revealed about temperature changes in the last 5 million years was both surprising and new, says Viereck-Götte, who calls the results "horrifying." The data suggests "the ice caps are substantially more mobile and sensitive than we had assumed."


By Hank Roberts (not verified) on 10 Mar 2007 #permalink

found here:

Re the latest release from the IPCC:
---- quote----
Change 3: Deleting a threat:
The scientists originally included this statement about changes caused by retreating glaciers:
enlargement and increased numbers of glacial lakes, with increased risk of outburst floods

The final draft wound up reading:
enlargement and increased numbers of glacial lakes
---- end quote -----

Anyone got anything new on drumlins?

By Hank Roberts (not verified) on 10 Apr 2007 #permalink

Jökulhlaups. With an umlaut.

Having learned that the whole issue is handled by this single word, I can let the subject rest.

Subglacial floods beneath ice sheets
IssueVolume 364, Number 1844 / July 15, 2006
Article TypeResearch-Article

G.W. Evatt1, A.C. Fowler 1, C.D. Clark 2, N.R.J. Hulton 3

1 Oxford University Mathematical Institute 24-29 St Giles', Oxford OX1 3LB, UK
2 University of Sheffield Department of Geography Winter Street, Sheffield S10 2TN, UK
3 University of Edinburgh School of Geosciences Drummond Street, Edinburgh EH8 9XP, UK


Subglacial floods (jökulhlaups) are well documented as occurring beneath present day glaciers and ice caps. In addition, it is known that massive floods have occurred from ice-dammed lakes proximal to the Laurentide ice sheet during the last ice age, and it has been suggested that at least one such flood below the waning ice sheet was responsible for a dramatic cooling event some 8000 years ago. We propose that drainage of lakes from beneath ice sheets will generally occur in a time-periodic fashion, and that such floods can be of severe magnitude. Such hydraulic eruptions are likely to have caused severe climatic disturbances in the past, and may well do so in the future.

By Hank Roberts (not verified) on 14 Jun 2007 #permalink

Lo! It's News! (Well, it's about Greenland, so I'm still just speculating that it's happening in Antarctica too, and happened underneath the continental glaciers elsewhere like in Idaho instead of water pooling on top of them as often pictured.)

Note per last line of the abstract that nobody has thought about this possibility til now :-)


(P.S., William, search on your blog page is still or again broken. Google for stoat scienceblog jokulhlaup
found the dusty old topic to add this. Good thing I remembered how to spell jokulhlaup.

GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L02503, doi:10.1029/2007GL031765, 2008

Channelized bottom melting and stability of floating ice shelves

E. Rignot

Earth System Science, University of California, Irvine, California, USA
Jet Propulsion Laboratory, Pasadena, California, USA

K. Steffen

Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA


The floating ice shelf in front of Petermann Glacier, in northwest Greenland, experiences massive bottom melting that removes 80% of its ice before calving into the Arctic Ocean. Detailed surveys of the ice shelf reveal the presence of 1-2 km wide, 200-400 m deep, sub-ice shelf channels, aligned with the flow direction and spaced by 5 km. We attribute their formation to the bottom melting of ice from warm ocean waters underneath. Drilling at the center of one of channel, only 8 m above sea level, confirms the presence of ice-shelf melt water in the channel. These deep incisions in ice-shelf thickness imply a vulnerability to mechanical break up and climate warming of ice shelves that has not been considered previously. ....

[Interesting, true, but losing 80% is an awful lot. It hardly matters if they break up after that :-) nb this can only apply to ice shelves, not the main ice sheet -W]

By Hank Roberts (not verified) on 19 Jan 2008 #permalink

William, which 'this'?

> this can only apply to ice shelves, not the main ice sheet

"this" -- the channels under the ice? Or the breakup?

[The channels. They are from oceanic heat: "We attribute their formation to the bottom melting of ice from warm ocean waters underneath" -W]

I'd think the channels observed out at the edges of the Greenland ice would likely have counterparts under the Antarctic -- the shape would seem to be from meltwater flowing out rather than melting along the edge from warm seawater.

I recall (maybe left links earlier above or in the old Prometheus thread) that liquid water has been described there from cameras lowered into boreholes to the base of the ice, in surprising large voids, and flows of water observed under the ice sheets would, I'd think, create similar channels.

Admittedly they won't be as easy to observe; I recall one unmanned sub was lost,

but don't see much new reported, though there are mentions of several new ones planned

By Hank Roberts (not verified) on 21 Jan 2008 #permalink


Robotic Telescope Installed on Antarctica Plateau
Posted by Zonk on Wednesday February 06, @03:44PM

Robotics Space Science

Reservoir Hill writes "Antarctica claims some of the best astronomical sky conditions in the world -- devoid of clouds with steady air that makes for clear viewing. The very best conditions unfortunately lie deep in the interior on a high-altitude plateau called Dome A. With an elevation of up to 4,093m, it's known as the most unapproachable point in the earth's southernmost region. Now astronomers in a Chinese scientific expedition have set up an experimental observatory at Dome A after lugging their equipment across Antarctica with the help of Australia and the US. The observatory will hunt for alien planets, while also measuring the observing conditions at the site to see if it is worth trying to build bigger observatories there. The observatory is automated, pointing its telescopes on its own while astronomers monitor its progress from other locations around the world via satellite link. PLATO is powered by a gas generator, and has a 4000-litre tank of jet fuel to keep it running through the winter. The observatory will search for planets around other stars using an array of four 14.5-centimetre telescopes called the Chinese Small Telescope Array (CSTAR). Astronomers hope to return in 2009 with new instruments, including the Antarctica Schmidt Telescopes (AST-3), a trio of telescopes with 0.5-metre mirrors, which will be more sensitive to planets than CSTAR."

By Hank Roberts (not verified) on 06 Feb 2008 #permalink

So, given that we know this:


and have reports about surface melting in Antarctica,

and now this:


... The paired surface temperature and gravity data confirm a strong connection between melting on ice sheet surfaces in areas below 6,500 feet in elevation, and ice loss throughout the ice sheet's giant mass. The result led Hall's team to conclude that the start of surface melting triggers mass loss of ice over large areas of the ice sheet.

The beginning of mass loss is highly sensitive to even minor amounts of surface melt. Hall and her colleagues showed that when less than two percent of the lower reaches of the ice sheet begins to melt at the surface, mass loss of ice can result. For example, in 2004 and 2005, the GRACE satellites recorded the onset of rapid subsurface ice loss less than 15 days after surface melting was captured by the Terra satellite.

The MODIS instrument acquired this image of melt ponds on Greenland's western coast in June, 2006. The MODIS instrument acquired this image of melt ponds on Greenland's western coast in June, 2006. The ponds appear as dark blue dots on the aqua blue background.

"We're seeing a close correspondence between the date that surface melting begins, and the date that mass loss of ice begins beneath the surface," Hall said. "This indicates that the meltwater from the surface must be traveling down to the base of the ice sheet -- through over a mile of ice -- very rapidly, where its presence allows the ice at the base to slide forward, speeding the flow of outlet glaciers that discharge icebergs and water into the surrounding ocean."

How will the modelers handle this behavior?

I recall this:

[Response: Dynamics are as important as thermodynamics here. Recent evidence (e.g. as reviewed by us a few months back) suggests that the demise of large parts of the major ice sheets could potentially take place far faster-on timescales of perhaps several centuries-due to the influence of ice sheet dynamics. For example, crevices at the surface of the ice sheet are now known to sometimes penetrate all the way down to the bottom of the ice sheet forming channels ("moulins") that allow surface meltwater to reach the bottom of the ice sheet, where it lubricates the ice, allowing it to stream into the ocean at velocities potentially far greater than once envisioned. These processes are still far from perfectly understood, because they require a representation of the fairly complicated rheology involved in ice sheet dynamics. But it appears far more likely that a better understanding of these processes will act to revised our estimates of ice sheet collapse timescales downward, rather than upward. - mike]


By Hank Roberts (not verified) on 23 Feb 2008 #permalink


Sunday, 24 February 2008, 00:24 GMT

Antarctic glaciers surge to ocean
By Martin Redfern
Rothera Research Station, Antarctica

---excerpts follow------

... the researchers spent most of their time driving skidoos across the flat, featureless ice.

"We drove skidoos over it for something like 2,500km each and we didn't see a single piece of topography."

Rob Bingham was towing a radar on a 100m-long line and detecting reflections from within the ice using a receiver another 100m behind that.

The signals are revealing ancient flow lines in the ice. The hope is to reconstruct how it moved in the past.
Throughout the 1990s, according to satellite measurements, the glacier was accelerating by around 1% a year. Julian Scott's sensational finding this season is that it now seems to have accelerated by 7% in a single season, sending more and more ice into the ocean.

"The measurements from last season seem to show an incredible acceleration, a rate of up to 7%. That is far greater than the accelerations they were getting excited about in the 1990s."

The reason does not seem to be warming in the surrounding air. ...

By Hank Roberts (not verified) on 23 Feb 2008 #permalink

A useful expert summary here:

Quoting in full, because it answers a lot of my questions in simple clear language of few syllables:

# Mauri Pelto Says:
28 April 2008 at 2:52 PM

Lakes form at the bottom of a glacier or on the surface. Because ice crystals deform under pressure, and pressure is substantial within a glacier or ice sheet it is not possible to have substantial void volumes. Ice under pressure would deform and flow into this void. This happens to much of the seasonal hydrology system each winter. Without water flow to keep tunnels open, they close, then in spring maximum water pressures often occur befor the conduit system redevelops. Once opened the flowing meltwater can maintain these narrow conduits. However, the meltwater does not have enough heat to melt much. At the base of the glaciers even in the summer next to these streams, you will see new ice coating the bedrock in places. The moulin ice riddling is science fiction. No ice sheet or glacier collapses due to riddling by moulins. I still see a persistent misconception about the ability of meltwater to melt glacier ice and riddle the glacier with holes. I work on glaciers with lots of melt and they are not weakened by all the meltwater drainage. The meltwater is not a very capable melter of ice. Ice is unlike rock which does not deform under the pressure and temperatures observed on glaciers.

By Hank Roberts (not verified) on 28 Apr 2008 #permalink

The ANDRILL ice cores should have been farmed out to researchers who should be writing and publishing papers on them Has anyone seen mention of these?

I found this:



in late 2006, the Andrill team discovered undisturbed deposits 15 kilometers (9 miles) outside the research station near the Mount Erebus volcano.

A first look at conditions that prevailed five million years ago

"This time we were able to drill into layers representing the period between five and 12 million years ago," Andrill team member and geologist Lothar Viereck-Götte told SPIEGEL ONLINE.

What these unique ice cores revealed about temperature changes in the last 5 million years was both surprising and new, says Viereck-Götte, who calls the results "horrifying." The data suggests "the ice caps are substantially more mobile and sensitive than we had assumed."

"The idea that the ocean here was ice-free for almost a million years is completely new," says Viereck-Götte. Besides, he adds, the melting that occurred about 5 million years ago can be seen in the context of a prehistoric climate shift.

According to Viereck-Götte, "massive melting" must have occurred in the Antarctic during the so-called Miocene-Pliocene warming. The cause sounds anything but massive. Based on isotope analyses from various locations worldwide, paleoclimatologists know that the average global temperature in the oceans increased by only two to three degrees Celsius (3.6-5.4 degrees Fahrenheit) -- a seemingly minor change. Nevertheless this change in temperature, according to the new Andrill ice core, led to an ice-free Ross Sea.

For researchers the clue lies in tiny microorganisms known as diatoms, which cannot survive in water that is covered by ice. But they were found in the core representing an uninterrupted period of 1 million years.

"We would never have thought that this system is so sensitive," says Viereck-Götte. The consequences of an ice-free Ross Sea would be far-reaching, not just for sea levels.

-----end excerpt--------

By Hank Roberts (not verified) on 29 Apr 2008 #permalink

"The Antarctic Geological Drilling (ANDRILL) programme has astonished scientists recently with evidence for periodic warm open waters in the Ross Sea up until as recently as 1 million years ago...."


Nature 451, 284-285 (17 January 2008) | doi:10.1038/nature06589; Published online 16 January 2008
Unlocking the mysteries of the ice ages
Maureen E. Raymo & Peter Huybers

By Hank Roberts (not verified) on 29 Apr 2008 #permalink

Actual science (abstract only)

Palaeogeography, Palaeoclimatology, Palaeoecology
Volume 260, Issues 1-2, 7 April 2008, Pages 245-261
Antarctic cryosphere and Southern Ocean climate evolution (Cenozoic-Holocene), 1) EGU Meeting, 2) XXIX SCAR Meeting

Retreat history of the Ross Ice Sheet (Shelf) since the Last Glacial Maximum from deep-basin sediment cores around Ross Island

R.M. McKay, G.B. Dunbar, T.R. Naish, P.J. Barrett, L. Carter and M. Harper

By Hank Roberts (not verified) on 29 Apr 2008 #permalink

Increasing Antarctic sea ice under warming atmospheric and oceanic conditions

Author(s): Zhang JL (Zhang, Jinlun)
Source: JOURNAL OF CLIMATE Volume: 20 Issue: 11 Pages: 2515-2529 JUN 1 2007 Times Cited: 1 References: 34
IDS Number: 177NH
ISSN: 0894-8755
DOI: 10.1175/JCLI4136.1

Abstract: Estimates of sea ice extent based on satellite observations show an increasing Antarctic sea ice cover from 1979 to 2004 even though in situ observations show a prevailing warming trend in both the atmosphere and the ocean. This riddle is explored here using a global multicategory thickness and enthalpy distribution sea ice model coupled to an ocean model. Forced by the NCEP-NCAR reanalysis data, the model simulates an increase of 0.20 x 10(12) m(3) yr(-1) (1.0% yr(-1)) in total Antarctic sea ice volume and 0.084 x 10(12) m(2) yr(-1) (0.6% yr(-1)) in sea ice extent from 1979 to 2004 when the satellite observations show an increase of 0.027 x 10(12) m(2) yr(-1) (0.2% yr(-1)) in sea ice extent during the same period. The model shows that an increase in surface air temperature and downward longwave radiation results in an increase in the upper-ocean temperature and a decrease in sea ice growth, leading to a decrease in salt rejection from ice, in the upper-ocean salinity, and in the upper-ocean density. The reduced salt rejection and upper-ocean density and the enhanced thermohaline stratification tend to suppress convective overturning, leading to a decrease in the upward ocean heat transport and the ocean heat flux available to melt sea ice. The ice melting from ocean heat flux decreases faster than the ice growth does in the weakly stratified Southern Ocean, leading to an increase in the net ice production and hence an increase in ice mass. This mechanism is the main reason why the Antarctic sea ice has increased in spite of warming conditions both above and below during the period 1979-2004 and the extended period 1948-2004.

[Yeah. Not sure I believe it though -W]

By Hank Roberts (not verified) on 22 Sep 2008 #permalink

This is wonderful, for those who like hardware that can go where no hardware has gone before. This is as much fun as the Mars Rover story:


Exploring beneath the PIG Ice Shelf with the
Autosub3 AUV

"... 60 km into the ice shelf cavity."
"... Autosub3 had run beneath the ice for almost 4 days and
for 510 km.... exploring the Pine Island Glacier, a floating
extension of the West Antarctic ice sheet ...."
"... The data collected by the
Autosub3 will help answer the question of whether the warm
water and rapid melting is responsible for the currently
observed thinning of the ice shelves in this region.
There are three specific objectives to the deployment of
Autosub 3 under the PIG:
⢠To map the seabed beneath the ice shelve.
⢠To map the underside of the ice shelve.
⢠To determine where and how heat is transferred from the
inflowing lower layer waters to the out flowing upper water.
The primary target was the Pine Island Glacier (PIG) Ice
Shelf, at around 75 degrees South, 101 degrees West."

[Hopefully it won't suffer the same terrible fate as autosub 2 did - W]

By Hank Roberts (not verified) on 22 Aug 2009 #permalink

This happens to much of the seasonal hydrology system each winter. Without water flow to keep tunnels open, they close, then in spring maximum water pressures often occur befor the conduit system redevelops.

Possibly of interest for climatologists planning vacations in the western USA:


Congress passed the bill to recognize the Ice Age Floods National Geologic Trail, and the President has signed it, as part of the Omnibus Public Lands Package back in May. This trail links dozens of important geologic localities (some of them already National Natural Landmarks) in a virtual park, linked by signage, road guides, and local businesses and organizations. It's a unique model for public parks, and now it will be allowed to set an example for geoparks elsewhere in the United States and the world.

The Ice Age Floods National Geologic Trail

Ice age floods


A bit more on topic -- William, do you know if there's a way to test floating sea ice and determine whether the water came from contemporary ocean water, or from glacial meltwater (melting off the bottom of floating ice tongues and promptly refreezing as the fresh water floats up to the surface at the edge)? I'd guess the oxygen isotope ratios can be used.

This might make sense of the commonly trumpeted "but Antarctic sea ice is increasing" point -- if we're getting significant melting at the bottom of the old ice pushing out into the warmer ocean and then quickly refreezing of that old fresh water around the edges.

[You can tell fronzen-sea-water ice from meteoric - ie, frozen snow - ice by the salt concentration. Sea ice rejects brine, but not all of it. Icebergs are even purer. However, melting ice shelves mix with the sea water so you would never see pure re-frozen ice shelf. The path from sub-ice-shelf-melt to surface is quite complex. Example http://www.agu.org/pubs/crossref/2007/2006JC003915.shtml (I shared an office with that Paul Holland once, you know). I'd point you at the BAS web site but I'd forgotten till just now just how rubbish it is. There is a pic in this: http://www.cpom.org/research/ph-frisp.pdf - its that Paul H again -W]

drumlins -- rapid rate of change rediscovered again for the first time ever once more! (or something like that).

Glacial ice used to be so reassuring, but now it's getting to seem creepy.


"Nov 18, 2010
The landform known as a drumlin, created when the ice advanced during the Ice Age, can also be produced by today's glaciers. This discovery, made by researchers from the University of Gothenburg, Sweden, has just been published in the scientific journal Geology....."