New results from an investigation into Antarctica’s potential contribution to sea level rise are reported this week (Sunday 20 June) by scientists from the British Antarctic Survey (BAS), Lamont-Doherty Earth Observatory (LDEO) and the National Oceanography Centre in the journal Nature Geoscience.
Thinning ice in West Antarctica is currently contributing nearly 10 per cent of global sea level rise and scientists have identified Pine Island Glacier (PIG) as a major source. As part of a series of investigations to better understand the impact of melting ice on sea level an exciting new discovery has been made. Using Autosub (an autonomous underwater vehicle) to dive deep and travel far beneath the pine Island Glacier’s floating ice shelf, scientists captured ocean and sea-floor measurements, which revealed a 300m high ridge (mountain) on the sea floor.
Pine Island Glacier was once grounded on (sitting on top of) this underwater ridge, which slowed its flow into the sea. However, in recent decades it has thinned and disconnected from the ridge, allowing the glacier to move ice more rapidly from the land into the sea. This also permitted deep warm ocean water to flow over the ridge and into a widening cavity that now extends to an area of 1000 km2 under the ice shelf. The warm water, trapped under the ice, is causing the bottom of the ice shelf to melt, resulting in continuous thinning and acceleration of the glacier.
Lead author Dr Adrian Jenkins of British Antarctic Survey said, “The discovery of the ridge has raised new questions about whether the current loss of ice from Pine Island Glacier is caused by recent climate change or is a continuation of a longer-term process that began when the glacier disconnected from the ridge.
“We do not know what kick-started the initial retreat from the ridge, but we do know that it started some time prior to 1970. Since detailed observations of Pine Island Glacier only began in the 1990s, we now need to use other techniques such as ice core analysis and computer modelling to look much further into the glacier’s history in order to understand if what we see now is part of a long term trend of ice sheet contraction. This work is vital for evaluating the risk of potential wide-spread collapse of West Antarctic glaciers.”
[UPDATE]
Steven Mosher has graciously allowed me to add my two cents worth here. As you know, I love data, it beats theories every time.
First, data on the location of the Pine Island Glacier:
Figure W1. Pine Island Glacier, Antarctica. The West Antarctic Peninsula is at the top right. Pine Island Glacier is shown by the snowflake. The white box outlines the area for which I show sea surface temperature (SST) below.
Next, data on the ocean surface temperatures. There are a couple of SST datasets that cover this area. Both are available at KNMI, that amazing resource. One is the Hadley HADISST Ice and Sea Surface Dataset. The other is the Reynolds satellite based dataset. Here’s what they say about the sea surface temperatures in the area outlined by the white box:
Figure W2. Change in sea surface temperature (SST) in the ocean off of Pine Island Glacier.
Conclusions? Well, it seems clear that the change in the sea surface temperature is not the reason for the melting of the Pine Island Glacier, SSTs have been dropping there for the last thirty years …
Regards to all,
w.
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“Current sea level rise has occurred at a mean rate of 1.8 mm per year for the past century, and more recently at rates estimated near 2.8 ± 0.4 to 3.1 ± 0.7 mm per year (1993-2003). ”
the statistic is about 7 years old.
But, we are still talking millimeters here. Silly millimeters per year. Benson & Hedges.
That should give pause for an extra moment at best.
It’ s not the sea-level rise that is of concern here, it’s the ice & cold from Antarctica escaping and lowering sea temps. Not to mention icebergs.
Sorry….but I thought there was recently a volcano discovered in that neighborhood, just west of the Pine Island glacier???
…or was it a cold volcano and doesn’t count??
June 21st. Happy Winter to the Southern Hemisphere. I look forward to an epic winter and all the good ice building it brings to Antarctica, not to mention the beneficial effects it has on humans down there. I also look forward to the solar minimum cooling lag time thread.
Antarctica’s circumpolar current and associated gyres
http://www.noc.soton.ac.uk/JRD/HYDRO/drake/gallery/acc.gif
are to certain extent impeded by the strong magnetic field in the area, the impediment being more effective to the warm saline currents (higher electric conductivity). Since the magnetic pole has been continuously growing weaker, and at the same time moving in the eastwards direction, the area of western peninsula is exposed to an unprecedented drop in the strength of magnetic field. As a result of these the warm saline currents velocity would be raising and hence bringing more and more warm waters.
http://www.vukcevic.talktalk.net/NFC8.htm
Hi Anthony and everyone. I know this is off topic, for which I apologize. But I wonder if Watt’s Up should cover this breaking story:
DK Makai and geologists worried about the potential for catastrophic Gulf Methane release:
http://www.huffingtonpost.com/dk-matai/gulf-of-mexico-danger-of_b_619095.html
BP– “what, me worry?” Haven’t we been so forthcoming all along? Trust us….
http://www.politicsdaily.com/2010/06/21/could-gulf-oil-leak-lead-to-methane-bubble-tsunami-bp-responds/
I think our friends on the Gulf coast may wish as calmly as possible to monitor this situation closely.
Best wishes and hoping this goes out with a whimper….
If 100% of the ice shelves on earth were to melt today, what would be the net rise in sea level? I’ve never seen an answer.
DJM –
http://www.livescience.com/environment/080120-antarctic-volcano.html
Maybe they should be trying to pull the strands together on this one . . . and also working out what the consequences of increased freshwater melt means for ocean temperatures downstream and the implications of that etc for the” whole general mish mash”.
Interesting website article on the “new” volcano: http://www.nsf.gov/news/news_summ.jsp?cntn_id=100385
Discovered in 2004.
“Highly sensitive temperature probes moving continuously across the bottom of the volcano revealed signs of geothermal heating of seawater. The heating was noticed especially near the edges of the feature where the freshest rock was observed.
These observations, along with historical reports from mariners of discolored water in the vicinity of the submerged peak, indicate that the volcano has been active recently.
“
-I wish more scientists would be honest and use those words more often.
– So it looks like started before the recent ‘alarming’ warming, in fact during the cold swing.
– Now they gone and spoilt it all. Why not carry on with observations? Measure it as Monckton would say. :o)
“This eruption occurred close to Pine Island Glacier on the West Antarctic Ice Sheet. The flow of this glacier towards the coast has speeded up in recent decades and it may be possible that heat from the volcano has caused some of that acceleration. However, it cannot explain the more widespread thinning of West Antarctic glaciers that together are contributing nearly 0.2mm per year to sea-level rise. This wider change most probably has its origin in warming ocean waters.”
From: http://www.antarctica.ac.uk/press/press_releases/press_release.php?id=341
if warming were causing the glacier to melt, it would retreat. it would eventualy fail to reach the ocean at all. i don’t see how you can even talk about a ‘glacier’ once it enters the sea. utter nonsense.
if the glacier continues to reach the sea, it is obviously gaining mass in the accretion zone. every real scientific article i have read by people who actually went to antarctica and measure real things has said antarctica is a net moisture sink. you think that would be obvious, too. but you can turn anything on it’s head with enough satellites and computer models.
“…..we now need to use other techniques such as ice core analysis and computer modeling……”
sigh, next up in the hit parade.
“…it started some time prior to 1970.”
Hair spray!
@ur momisugly peterhodges: A glacier is a “river” of ice – it flows (in this case into the ocean).
Here is an animation of the 2007 Pine Island iceberg calving: http://www.esa.int/esaEO/SEM9C9JJX7F_index_0.html
“We do not know what kick-started the initial retreat from the ridge, but we do know that it started some time prior to 1970”
So the “event”- whatever it was started before the period which the IPCC attribute to AGW.
It’s worse than we thought- AGW has been going on since before 1970!
These guys are just amateurs.
A REAL scientist would have done more exploration into the method by which human activity caused this to begin. They should have consulted the hockey team. And no matter what the actual result is, they failed to emphasize that unless we pass Cap and Trade immediately, all of the islands in the Antarctic will melt, causing sea level to rise at about a meter per month… later followed by the obligatory “it’s worse than we thought”.
(ps. Good to see what appears to be some real science still going on!)
vukcevic says: June 21, 2010 at 11:26 am
Antarctica’s circumpolar current and associated gyres are to certain extent impeded by the strong magnetic field in the area
There are also magnetic field changes in the Arctic too.
As a result of these the warm saline current of the Greenland’s branch of the North Atlantic current’s velocity is raising and hence bringing more warm waters to Greenland and a temperature rise.
In contrast the warm current’s velocity along the North Siberian coast is falling, as consequence the temperature is falling too.
See illustration at:
http://www.vukcevic.talktalk.net/NFC1.htm
Kevin.
melting ice shelves do not rise sea level because the ice was already floating (there might be a non significant increase in sea level because a given mass of liquid water has more volume than the same mass in a frozen state). Their only potential for sea level rise is that their disappearance (or faster flow into the sea) might accelerate the gravitational advance of land ice into the sea. Some observations by Steig and Vaugham in different arts of Antarctica suggest that land ice slides more easily towards the sea when adjoining ice shelves are thinner or disappear.
The net balance, however, requires computing annual ice accretion (mainly in the Antarctic hinterland) and ice melting. Global warming is predicted (by the IPCC) to increase precipitation over Antarctica, and that precipitation would turn into ice since summer temperatures are deep below zero everywhere (except in some summers at the tip of the Antarctic peninsula extending towards South America). Average annual temperature over Antarctica as a whole is -57°C.
Alan Cheetham says:
June 21, 2010 at 12:23 pm
@ur momisugly peterhodges: A glacier is a “river” of ice – it flows (in this case into the ocean)…
thanks alan. that was kind of my point, once a glacier reaches the ocean you expect things like calving. it is a completely different dynamic unrelated to how they are formed and move on land.
i am plenty aware of how glaciers behave. i just wonder if many of these ‘scientists’ are. any talk of ‘thinning’ has nothing to do with warming
If glaciers are melting – what can ice cores say about the history of the melt since the most important information is gone – melted away.
a floating glacier is still floating ice. It has already displaced the water that it would if it was all melted. There won’t be any increase in ocean levels when those floating glaciers detach and melt away.
Rhoda asks: “If glaciers are melting – what can ice cores say about the history of the melt since the most important information is gone – melted away.”
The melting concerned in this thread is in the floating ice shelves along the coast. And they have not melted away: there is only some regular flow towards the sea and the occasional calving of some chunks. Ice cores are extracted inland, in deep ice that has not melted for many millennia.
Can someone please explain where “deep warm water” came from?
Antarctica is earth’s ice cube making machine. Period.
How I wish I could post some photos of the frozen sea around Cape Town taken on 19/06/2010.
People could walk out on frozen sea water over 100 meters.
The barriers on the promenade are veiled in frozen seawater.