Global Warming on West Antarctic Ice Sheet three times the global average

Original article from San Fransisco Bay Area Indymedia, Dec 23rd, 2012 7:16 PM: The West Antarctic Ice Sheet is warming at three times the global average, according to temperature measurements at Byrd Polar Station. This has implications for the melting of the West Antarctic Ice sheet (WAIS) and sea level rise.

 

Related: Global warming in Antarctica: Thwaites and Pine Island Glaciers | Waking the giant: Global Warming in the Weddell Sea | Southern Ocean warming impact on Antarctic Ice Sheet and global sea level

The West Antarctic Ice Sheet is inherently unstable due to it's grounding in a deep depression below sea level. Warm Southern ocean currents are already reducing ice shelves holding back ice discharge from glaciers. As these ice shelves are undermined and break up it will allow significant acceleration of glacier discharge increasing the rate of sea level rise.

Lead study author David H. Bromwich from Ohio State University said:

"Our record suggests that continued summer warming in West Antarctica
could upset the surface mass balance of the ice sheet, so that the
region could make an even bigger contribution to sea level rise than it
already does," said Bromwich.

"Even without generating significant mass loss directly, surface melting
on the WAIS could contribute to sea level indirectly, by weakening the
West Antarctic ice shelves that restrain the region's natural ice flow
into the ocean."

This new study published in Nature Geoscience - Central West Antarctica among the most rapidly warming regions on Earth
- shows that a significant warming trend over the last 50 years has
been occurring at the top of the ice sheet at Byrd Polar Station. The
study confirms an earlier study by Steig et al published in 2009 in
Nature: Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year which was met with some degree of scientific scepticism. According to Eric Steig writing on Real Climate Blog: The heat is on in West Antarctica -

 

"they do more than back-up our results: they show that our estimates
were too conservative and that West Antarctica is actually warming by
about a factor of two more than we estimated. They also agree with the
key interpretation of the results that both we and David Schneider and
colleagues at NCAR have presented: that in the winter and spring
seasons, when the most rapid warming is occurring in West Antarctica,
the driver has been changes in the tropical Pacific, not the ozone hole
(which is invoked too frequently, in my view, to explain everything from
penguin populations to sea ice changes)."

 

Increasing Sea Surface temperatures in tropical pacific impacting West Antarctica

A 2011 paper in Nature Geoscience - Winter warming in West Antarctica caused by central tropical Pacific warming (abstract)
- details how sea surface temperatures in the tropical pacific are
contributing to the idespread warming trend in West Antarctica:

"recent warming in continental West Antarctica is linked to sea surface
temperature changes in the tropical Pacific. Over the past 30 years,
anomalous sea surface temperatures in the central tropical Pacific have
generated an atmospheric Rossby wave response that influences
atmospheric circulation over the Amundsen Sea, causing increased
advection of warm air to the Antarctic continent. General circulation
model experiments show that the central tropical Pacific is a critical
region for producing the observed high latitude response. We conclude
that, by affecting the atmospheric circulation at high southern
latitudes, increasing tropical sea surface temperatures may account for
West Antarctic warming through most of the twentieth century."

Most polar research stations are scattered around the edges of
Antarctica, with a couple located in central East Antarctica including
the US South Pole base. Byrd Polar Station is unusual in being the only
place measuring changes in the centre of West Antarctica. For most of
the time the base is unpopulated taking automated measurements.

Study co-author Andrew Monaghan from the National Center for Atmospheric
Research (NCAR) said that this now places West Antarctica as one of the
fastest arming regions on the planet.

"We've already seen enhanced surface melting contribute to the breakup
of the Antarctic's Larsen B Ice Shelf, where glaciers at the edge
discharged massive sections of ice into the ocean that contributed to
sea level rise," Monaghan said. "The stakes would be much higher if a
similar event occurred to an ice shelf restraining one of the enormous
WAIS glaciers."

It is estimated that the West Antarctic ice sheet currently contributes
0.3 mm to sea level rise each year. behind Greenland's present
contribution of 0.7 mm per year.

The Byrd Polar Research station was established in 1957, but was not
constantled populated. An automated weather station as installed in
1980, but experienced poer outages through the long polar winter due to
it's reliance on solar panels recharging the batteries powering the
station. Up to a third of the temperature record as missing due to these
problems. The researchers had to use corrected data from a computer
atmospheric model and a numerical analysis method to fill in the missing
observations.

The temperature analysis offers a more complete picture of warming in
West Antarctica. Bromwich said the results show more observations are
needed in the region.

"West Antarctica is one of the most rapidly changing regions on Earth,
but it is also one of the least known," he said. "Our study underscores
the need for a reliable network of meteorological observations
throughout West Antarctica, so that we can know what is happening--and
why--with more certainty."

 

Ice Sheet Melting is Non-linear, multi-metre sea level rise possible

So now the Arctic, Antarctic Peninsula and West Antarctica are showing
strong trends of global warming. This does not bode well for the
Greenland and West Antarctic Ice sheets, and will probably result in
their dissolution.

But a drastic reduction in CO2 emissions we may yet control the rate of
dissolution and the rate of sea level rise. Dissolution and melting of
ice sheets is a non-linear response to global warming, and may occurr at
a rapidly accelerating pace. This article on Climate State website says
sea level rise of 1 to 3 metres (or more) within the next 50 years is possible.
This article quotes as one of it's sources Hansen et al. from a 2011
Andre Glickson paper - Climate change: a warning from the past
(PDF):

 

"... amplifying feedbacks make ice sheet disintegration necessarily
highly non-linear. In a non-linear problem, the most relevant number for
projecting sea level rise is the doubling time for the rate of mass
loss. Hansen (2007) suggested that a 10-year doubling time was
plausible, pointing out that such a doubling time from a base of 1 mm
per year ice sheet contribution to sea level in the decade 2005-2015
would lead to a cumulative 5 m sea level rise by 2095."

Sources

  • Eurekalert - Media Release from Ohio State University, 23 December 2012 - Study shows rapid warming on the West Antarctic Ice Sheet
  • David H. Bromwich, Julien P. Nicolas, Andrew J. Monaghan,
    Matthew A. Lazzara, Linda M. Keller, George A. Weidner, & Aaron B.
    Wilson, Central West Antarctica among the most rapidly warming regions on Earth (abstract) , Nature Geoscience (2012) doi:10.1038/ngeo1671
  • Eric Steig, Real Climate, 23 December 2012, The heat is on in West Antarctica
  • Steig, E.J., Schneider, D.P. Rutherford, S.D., Mann, M.E., Comiso, J.C., Shindell, D.T. Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year, Nature 457, 459-462, doi:10.1038/nature07669 (2009).
  • Image Caption: Researchers at Ohio State University and their
    colleagues have discovered that the central region of the West Antarctic
    Ice Sheet (WAIS) is experiencing twice as much warming as previously
    thought.  Credit: Image by Julien Nicolas, courtesy of Ohio State
    University.