Recent Ice Sheet Growth in the Interior of Greenland
Climate scientists from Bergen have published a paper on October 20th Science Express, (which previews elected papers before publication in Science). They report growth estimated to be about 6 cm per year during the study period, 1992–2003 of the Greenland Ice sheet..
Climate change debates have promoted these studies using satellite data over the last 11 years – a much
hyped publicised sea level increase of 7 metres would result from the Greenland Ice field melting. This process, expected on a millennial time scale, should begin upon crossing the critical threshold for surface air temperature increase (~3ºC) for Greenland, predicted to happen before the end of this century.
Second, increased Greenland Ice Sheet melt and freshwater input into the northern North Atlantic Ocean is theorized to weaken the Gulf Stream at high latitudes and possibly even disrupt the global thermohaline circulation on a relatively rapid, multi-decadal time scale.
Johannessen and co-workers attribute the observed growth in the interior of the Greenland due to increased snowfall brought about by variability in the regional atmospheric circulation, the so-called North Atlantic Oscillation (NAO) phenomenon.i.e snow in winter.
Using their ice-sheet elevation estimates, the known NAO, the researchers established, for the first time, a direct relationship between Greenland Ice Sheet elevation change and the NAO. i.e snow in winter.
Elevation changes during winter were found to be negatively correlated (–0.88) to the winter NAO index, explaining about three quarters of the elevation changes.
Therefore, strongly negative NAO-index conditions lead to increased accumulation and elevation change during wintertime and vice versa.
The strong correlation between winter elevation changes and the NAO index, suggests a previously underappreciated role of the winter season and the NAO for elevation changes – a wildcard in Greenland Ice Sheet mass-balance scenarios under global warming.
In other words, observed phenomena do not fit the extrapolations of the Global Warming theory – It is interesting therefore to consider the views of the much loved IPCC (Acronym for Scientific jihad against Industrial development) in seeking to explain the mission of NASA’s ICE Satellite.
A key category of scientific uncertainty identified by the IPCC is "Polar ice sheets which affect predictions of global sea level change".Early commencement is needed to establish a baseline on ice balance beforegreenhouse warming becomes more significant.
It is not known whether Greenland and Antarctic ice sheets are growing or shrinking (uncertainty is +- 30% of mass input = +- 5 cm/yr averageice thickness = +- 2.3 mm/yr global sea level change). ICESat will measure< 1 cm/yr average ice thickness change ( < 5% of mass input and <0.4 mm/yr global sea level change).
It is not known whether future changes in mass balance associatedwith climate warming will be positive or negative (sensitivity perhaps- 10% to + 20% change in mass input/K temperature change = +0.8 mm/yr/Kto - 1.6 mm/yr/K sea level change). ICESat should measure changes inmass balance expected for 1 K polar warming (depends on sensitivity estimate).
Regrettably EU’s CRYOsat didn’t achieve lift off so their plans to measure polar ice caps will not be available for some time (see previous posting) … try 5 years.
Meanwhile here is a picture of the very cold Greenland interior © Petter Bjorstad, Bergen, Norway.
Recent blogs on same topic here