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Antarctic Ice Mass Growing – New NASA Study

October 31, 2015
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By Paul Homewood  

 

h/t Ben

 

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http://www.nasa.gov/feature/goddard/nasa-study-mass-gains-of-antarctic-ice-sheet-greater-than-losses

 

Hot off the press from NASA:

 

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A new NASA study says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.

The research challenges the conclusions of other studies, including the Intergovernmental Panel on Climate Change’s (IPCC) 2013 report, which says that Antarctica is overall losing land ice.

According to the new analysis of satellite data, the Antarctic ice sheet showed a net gain of 112 billion tons of ice a year from 1992 to 2001. That net gain slowed   to 82 billion tons of ice per year between 2003 and 2008.

“We’re essentially in agreement with other studies that show an increase in ice discharge in the Antarctic Peninsula and the Thwaites and Pine Island region of West Antarctica,” said Jay Zwally, a glaciologist with NASA Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study, which was published on Oct. 30 in the Journal of Glaciology. “Our main disagreement is for East Antarctica and the interior of West Antarctica – there, we see an ice gain that exceeds the losses in the other areas.”  Zwally added that his team “measured small height changes over large areas, as well as the large changes observed over smaller areas.”

Scientists calculate how much the ice sheet is growing or shrinking from the changes in surface height that are measured by the satellite altimeters. In locations where the amount of new snowfall accumulating on an ice sheet is not equal to the ice flow downward and outward to the ocean, the surface height changes and the ice-sheet mass grows or shrinks.

But it might only take a few decades for Antarctica’s growth to reverse, according to Zwally. “If the losses of the Antarctic Peninsula and parts of West Antarctica continue to increase at the same rate they’ve been increasing for the last two decades, the losses will catch up with the long-term gain in East Antarctica in 20 or 30 years — I don’t think there will be enough snowfall increase to offset these losses.”

The study analyzed changes in the surface height of the Antarctic ice sheet measured by radar altimeters on two European Space Agency European Remote Sensing (ERS) satellites, spanning from 1992 to 2001, and by the laser altimeter on NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) from 2003 to 2008.

Zwally said that while other scientists have assumed that the gains in elevation seen in East Antarctica are due to recent increases in snow accumulation, his team used meteorological data beginning in 1979 to show that the snowfall in East Antarctica actually decreased by 11 billion tons per year during both the ERS and ICESat periods. They also used information on snow accumulation for tens of thousands of years, derived by other scientists from ice cores, to conclude that East Antarctica has been thickening for a very long time.

“At the end of the last Ice Age, the air became warmer and carried more moisture across the continent, doubling the amount of snow dropped on the ice sheet,” Zwally said.

The extra snowfall that began 10,000 years ago has been slowly accumulating on the ice sheet and compacting into solid ice over millennia, thickening the ice in East Antarctica and the interior of West Antarctica by an average of 0.7 inches (1.7 centimeters) per year. This small thickening, sustained over thousands of years and spread over the vast expanse of these sectors of Antarctica, corresponds to a very large gain of ice – enough to outweigh the losses from fast-flowing glaciers in other parts of the continent and reduce global sea level rise. 

Zwally’s team calculated that the mass gain from the thickening of East Antarctica remained steady from 1992 to 2008 at 200 billion tons per year, while the ice losses from the coastal regions of West Antarctica and the Antarctic Peninsula increased by 65 billion tons per year.

“The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 millimeters per year away,” Zwally said. “But this is also bad news. If the 0.27 millimeters per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for.”

“The new study highlights the difficulties of measuring the small changes in ice height happening in East Antarctica,” said Ben Smith, a glaciologist with the University of Washington in Seattle who was not involved in Zwally’s study.

"Doing altimetry accurately for very large areas is extraordinarily difficult, and there are measurements of snow accumulation that need to be done independently to understand what’s happening in these places,” Smith said.

To help accurately measure changes in Antarctica, NASA is developing the successor to the ICESat mission, ICESat-2, which is scheduled to launch in 2018. “ICESat-2 will measure changes in the ice sheet within the thickness of a No. 2 pencil,” said Tom Neumann, a glaciologist at Goddard and deputy project scientist for ICESat-2. “It will contribute to solving the problem of Antarctica’s mass balance by providing a long-term record of elevation changes.”

http://www.nasa.gov/feature/goddard/nasa-study-mass-gains-of-antarctic-ice-sheet-greater-than-losses

 

As I have repeatedly said in the past, we have very little idea of what is happening with ice mass in the Antarctic, though scientists pretend they do. Above all, we think we can identify trends from a handful of years of observation.

We have had a succession of studies, each giving different conclusions. Now this one comes along and overturns the lot of them.

What is interesting though is this comment:

 

Zwally said that while other scientists have assumed that the gains in elevation seen in East Antarctica are due to recent increases in snow accumulation, his team used meteorological data beginning in 1979 to show that the snowfall in East Antarctica actually decreased by 11 billion tons per year during both the ERS and ICESat periods.

 

As Zwally states, at the end of the last Ice Age, the air became warmer and carried more moisture across the continent, doubling the amount of snow dropped on the ice sheet. The fact that snowfall has decreased since 1992 is strong evidence of a colder atmosphere. But even despite this decrease in snowfall, there is still enough of it to more than offset glacier melt.

The discovery also suggests that glacier melt from West Antarctica is nothing new, but has been going on for centuries. If it had not, the build up of snow in East Antarctica would have resulted in sea levels falling in the past.

 

The press release is full of if, buts and maybes, in terms of how we’

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11 Comments
  1. Joe Public permalink
    October 31, 2015 1:45 pm

    Sorry, but won’t believe it until the BBC doesn’t report it. 😀

    “Still, areas of the continent, like the Antarctic Peninsula photographed above, have increased their mass loss in the last decades.” An author paid by the word?

    What’s wrong with: “Still, areas of the continent, like the Antarctic Peninsula photographed above, have lost mass in the last decades.”?

    • November 1, 2015 7:15 am

      Em maybe cos ” increased their mass loss” means on average the rate each year at which they lose mass has increased.

  2. October 31, 2015 4:52 pm

    “The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 millimeters per year away,” Zwally said. “But this is also bad news. If the 0.27 millimeters per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for.” Jay Zwally

    “Doing altimetry accurately for very large areas is extraordinarily difficult, and there are measurements of snow accumulation that need to be done independently to understand what’s happening in these places…” Ben Smith

    Good news and bad news based on 1/4 of a millimeter. No uncertainties stated in the article. And they’re not sure of it’s sign.

    Good / bad news? it’s no news, because we have no idea.

    Settled science indeed.

  3. Bloke down the pub permalink
    October 31, 2015 6:42 pm

    The discovery also suggests that glacier melt from West Antarctica is nothing new, but has been going on for centuries. If it had not, the build up of snow in East Antarctica would have resulted in sea levels falling in the past.

    Both coral reefs and mankind can cope much easier with rising sea levels cf falling sea levels.

  4. kennethrichards permalink
    November 1, 2015 6:31 am

    In the subsections of the ice sheet where there is overall melt – namely on portions of the West Antarctic Ice Sheet – the mass losses can predominantly be explained by geothermal (subsurface) heat flux, as these scientists indicate:

    —–

    http://advances.sciencemag.org/content/advances/1/6/e1500093.full.pdf

    The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the West Antarctic Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m2, significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m2. The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region.

    —–

    http://www.sciencemag.org/content/309/5733/464.short

    The geothermal heat flux is an important factor in the dynamics of ice sheets; it affects the occurrence of subglacial lakes, the onset of ice streams, and mass losses from the ice sheet base. Because direct heat flux measurements in ice-covered regions are difficult to obtain, we developed a method that uses satellite magnetic data to estimate the heat flux underneath the Antarctic ice sheet. We found that the heat flux underneath the [Antarctic] ice sheet varies from 40 to 185 megawatts per square meter and that areas of high heat flux coincide with known current volcanism and some areas known to have ice streams.

    —–

    Geothermal heat is also known to be a dominant source of melting rates on the Greenland ice sheet. The heat flux for subsurface melting at both poles is orders of magnitude greater than the alleged total forcing (1.68 W/m-2) attributed to CO2 for 1750 to present.

    —–
    http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.73.3040&rep=rep1&type=pdf
    High Geothermal Heat Flow, Basal Melt, and the Origin of Rapid Ice Flow in Central Greenland
    Age-depth relations from internal layering reveal a large region of rapid basal melting in Greenland. Melt is localized at the onset of rapid ice flow in the large ice stream that drains north off the summit dome and other areas in the northeast quadrant of the ice sheet. Locally, high melt rates indicate geothermal fluxes 15 to 30 times continental background. The southern limit of melt coincides with magnetic anomalies and topography that suggest a volcanic origin
    —–
    http://onlinelibrary.wiley.com/doi/10.1029/2007GL030046/full
    Introduction: [T]here is a growing body of evidence suggesting more extensive basal melting in the central region of northern Greenland. Fahnestock et al. [2001a] determined age-depth relationships and basal melt rate from ice-penetrating radar in northern Greenland and detected high basal melt, in places up to 0.2 m/yr, under the onset region of the Northeast Ice Stream and its southern tributaries. This basal melt requires a geothermal heat flux much greater than the estimated continental background of 57 mW/m2 [Sclater et al., 1980] and Fahnestock et al. [2001a] speculate that the inferred large heat flow may be of volcanic origin. Similarly, at the base of the NGRIP deep ice core, drilled on the ice divide 170 km northwest of the onset region of the Northeast Ice Stream, the observed basal temperature is at the pressure-melting point [Anderson et al., 2004; Dahl-Jensen et al., 2003]. The basal melt rate at NGRIP reaches 7.5 mm ice per year, and the modeled geothermal heat flux is between 90 and 160 mW/m2 along the flow line originating 50 km upstream of the drill site [Dahl-Jensen et al., 2003]. Again, the origin of the large geothermal heat flux remains unidentified. Ice-penetrating radar profiles show bright bed reflections in many locations in northern Greenland, indicating the presence of lubricating meltwater at the glacier base.
    —–
    http://www.researchgate.net/publication/233542206_Estimating_the_basal_melt_rate_at_NorthGRIP_using_a_Monte_Carlo_technique
    From radio-echo sounding (RES) surveys and ice core data it can be seen that the ice sheet is melting at the base in a large area in Northern Greenland. The RES images reveal internal layers in the ice. The layers are former deposition surfaces and are thus isochrones. Undulations of the isochrones in regions where the base is smooth suggest that the basal melt rate changes over short distances. This indicates that the geothermal heat flux is very high and has large spatial variability in Northern Greenland…. Combining the estimated basal melt rates with the observed borehole temperatures allows us to convert the basal melt rates to geothermal heat flow values. From the two-dimensional model we find the basal melt rate and geothermal heat flux at NorthGRIP to be 6.1 mm a−1 and 129 mW m−2, respectively.
    —–
    http://www.researchgate.net/publication/233650679_Basal_melt_at_NorthGRIP_modeled_from_borehole_ice-core_and_radio-echo_sounder_observations
    From temperature measurements down through the 3001 m deep borehole at the North Greenland Icecore Project (NorthGRIP) drill site, it is now clear that the ice at the base, 3080 m below the surface, is at the pressure-melting point. This is supported by the measurements on the ice core where the annual-layer thicknesses show there is bottom melting at the site and upstream from the borehole. … The results show the geothermal heat flow varies from 50 to 200 mW m-2 along the 100 km section of the modeled flowline. The melt rate at the NorthGRIP site is 0.75 cm a-1, but the deep ice in the NorthGRIP core originated 50 km upstream and has experienced melt rates as high as 1.1 cm a-1.

    • John, UK permalink
      November 1, 2015 11:58 am

      Thanks for your comments and linked references, very useful indeed.

  5. November 1, 2015 7:26 am

    So the NASA PR blog finally does a story where it doesn’t spin it for the full climate alarm catastrophe angle. If you look at the headlines listed on the left hand side of the page marked RELATED ..you can see they normally do an a climate ice hype story every 2weeks.

    – I guess with this new research there was no other way to play it rather than straight..They can’t push for a disaster angle on it.

  6. November 1, 2015 10:47 am

    Reblogged this on WeatherAction News.

  7. CheshireRed permalink
    November 1, 2015 11:57 am

    It only seems like last month when the Guardian was howling from the rooftops about ‘irreversible and catastrophic’ 20 foot sea level rises caused by the ‘collapsing’ Antarctic.
    Now NASA themselves flatly contradict those absurd headlines. Will they retract their scaremongering? There’s more chance of Al Gore swimming to the moon.

  8. November 1, 2015 1:17 pm

    From my own archives, an “Surprise! There’s an active volcano under Antarctic ice” from January 22, 2008 by Anthony Watts (Wattsupwiththt). “Scientists have discovered” a string of active volcanoes under the Antarctic ice sheet the “create melt-water that lubricates the base of the ice sheet and increases the flow towards the sea.” You will be shocked, shocked, I say to learn that one under the West Antarctic Ice Sheet has been erupting for the past 2000 years.

    http://wattsupwiththat.com/2008/01/22/surprise-theres-an-active-volcano-under-antarctic-ice/

  9. Jerry Greenwood permalink
    November 2, 2015 6:34 pm

    It now looks like conditions in Antarctica are in a constant state of flux. It’s nice to see the science is catching up with two hundred years of observation.

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