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Home | Space, Earth & Ocean | The Nansen Group, The advent of the Blue Arctic Ocean
 

Predicting the advent of the Blue Arctic Ocean

The Nansen Group

 
The Nansen Center’s Group
Leader Ola M. Johannessen

  • Bergen, Norway, Director Ola M. Johannessen, est. 1986
  • St. Petersburg, Russia, Director Leonid P. Bobylev, est. 1992
  • Cochin, India, Director Ajith Joseph, est. 1999
  • Beijing, China, Director Hui-Jun Wang, est. 2003.
   

The Nansen Group consists of four centres globally. They are non-profit research institutes which conduct basic and applied environmental research on understanding, monitoring and forecasting of the world’s local, regional and global environment and climate, and their impact on society.

Using ice as an indicator

Sea ice extent is a widely used and well-constrained metric for summarising the state of the climate system. The decrease of sea ice extent and area was addressed by Nansen Environmental and Remote Sensing Center (NERSC) in 1995. It was established that the ice extent, defined as more than 15% ice concentration in the Arctic, decreased by 3% per decade, with no trend for Antarctica.

This analysis was based on data from United States (US) microwave satellites. These have been the “work horse” for ice research since November 1978, when the NASA Nimbus 7 satellite was launched, followed by several other US microwave satellites. In 1999, NERSC established for the first time that the multi year ice, defined as the ice which survives the summer melt, decreased by 7% per decade, double the total ice extent. The first year ice is typical 1-2m thick while the multi year is typical 3-4m thick.

Fig 1: Arctic sea-ice extent and CO2
(a) Time series of annual arctic sea-ice extent and atmospheric concentrations of CO2 for 1900-2007. Sea-ice observations are from the Walsh and Chapman dataset 1900-78, merged with sea-ice concentration retrieved from satellite passive-microwave data (1979-2007) using the NORSEX algorithm, with ice extent updated to 2007. The CO2 scale is inverted.
Fig 1: Arctic sea-ice extent and CO2
(a) Time series of annual arctic sea-ice extent and atmospheric concentrations of CO2 for 1900-2007. Sea-ice observations are from the Walsh and Chapman dataset 1900-78, merged with sea-ice concentration retrieved from satellite passive-microwave data (1979-2007) using the NORSEX algorithm, with ice extent updated to 2007. The CO2 scale is inverted.

In 2004 NERSC showed by use of coupled global climate models that the ice cover would melt during the summer time under a doubling of the CO2 concentration in the atmosphere. If not, drastic reduction of CO2 will be enforced and this may happen well before the end of this century. The latest prediction by some of the Intergovernmental Panel on Climate Change (IPCC) coupled global climate models, indicate that the summer ice will melt before 2050. NERSC has also updated the decreasing trend of the ice extent and multi year ice to 3-4% and 7-9% per decade respectively. See also the Arctic-Roos public ice information system, coordinated by the Nansen Center (www.arctic-roos.org).

(b) Scatterplot and regression lines indicate the correlation of CO2 and sea-ice extent for the periods 1961-85 (blue) and 1986-2007 (red). The regression line (green) for 1961-2007 is sea-ice extent = -0.030× CO2 + 22.97, r2 ~ 0.90.
(b) Scatterplot and regression lines indicate the correlation of CO2 and sea-ice extent for the periods 1961-85 (blue) and 1986-2007 (red). The regression line (green) for 1961-2007 is sea-ice extent = -0.030× CO2 + 22.97, r2 ~ 0.90.

In 2008, NERSC discovered that the decreasing Arctic sea ice extent mirrors increasing CO2 on a decadal time scale from 1900 up to 2008 (figure 1). The correlation between these two variables was -0,95, indicating that 90% (r²= 0,90) of the decreasing ice extent could be explained by increased CO2.

Fig 2: Arctic sea ice in the 20th and 21st centuries.
Fig 2: Arctic sea ice in the 20th and 21st centuries.

Annual sea-ice extent 1900-2007 (observed: green, and IPCC modelled mean ensemble: black) and predictions for 2007-50 under IPCC projected CO2 scenarios. The ensemble mean of 15 IPCC numerical-model experiments are thick lines: B1: blue; A2: red.
Shading indicates ±1 s.d. uncertainty.

Projections based on empirical relationship are thin lines, B1: blue; A2: red. The projections are based on a linear regression of CO2 and sea-ice extent data from 1961-2007. The empirical projection does not include natural fluctuations that would be superposed on the trends, as seen in the observations (green).

The derived statistical relation, Sea Ice Extent = -0.030x CO2 +22,97 on the B1 and A2 CO2 scenario, showed the sea ice extent was several million km² less than that predicted by the IPCC models for 2050 (figure 2). Furthermore, using the above statistical equation and setting the ice equal zero and solving for CO2, the result is that all ice, both summer and winter, will disappear when the CO2 equals 765 ppmv. It is then that the Blue Arctic Ocean will appear.

The Nansen Group
W: nersc.no/~olam/omj.html

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