Paleoclimate studies on Antarctic blue ice fields with ground- penetrating radar
Leader: John Moore Start of the project: 1999
Research group: Global change End of the project: 2001 (continued 2002-2005)
| Central research questions were:
• How are glaciers in Antarctica behaving now?
• What do ice cores from Antarctica tell us about climate history?
• What will changing climate do to glaciers in the polar regions?
We focused our research on mountainous regions of Antarctica where the wind continuously blows away and snow fall, this leads to bare ice being exposed at the surface - these are called "Blue Ice Areas". This ice has flowed up from below where it was buried many kilometers and centuries ago up stream, and is now at the surface. This ancient ice provides a valuable archive of the past climate of the region that we analyzed using sensitive chemical methods in our clean rooms in Rovaniemi.
However, the great difficulty is to know the actual age of this blue ice. We formalized and compared three methods of determining both the surface age gradient of the blue ice and the dip angles of isochrones in the firn/blue ice transition zone: observed and dated radar internal reflections, geometrical model of isochrones and output from a flowline model. The geometrical analysis provides generally applicable relationships between ice surface velocity and surface-age gradient or isochrone dip angle. This has also been applied to other areas.
During the fieldwork, ice and snow samples were taken from 5 different Blue Ice Areas including a 100 m long horizontal ice core. This core is estimated to represent a 1000 year period of climate history between 4 000-10 000 B.P. The chemical analyses were completed.
Blue ice research in Antarctica.
Photo: John Moore
The most important scientific results
Ice chemistry and isotopic data are now available on a 100 m long section of ice the blue ice area near Svea. Unexpectedly the ice was only about 10 000 years old. This however allowed us to refine our sampling strategy and produce a much better age model for the area.
Ice flow models have been made of blue ice areas both in Dronning Maud Land and in West Antarctica. The model was published in Geophysical Research Letters, 2003. The model can be applied outside blue ice areas as well. It is presently being applied to valley glaciers in Svalbard.
Generally applicable relationships between ice surface velocity and surface-age gradient or isochrone dip angle were found using the field data and the computer model. The results were published in Annals of Glaciology in 2004.
A 100 m long horizontal ice core was collected in the field season 2003-2004. The age of the samples is estimated to be 20 000 – 40 000 years based on the flow model. The chemical analysis started in summer 2004.
A new instrument for electromagnetic mapping was built and was successfully used to map the blue ice for climate boundaries. This instrument has potential to be successfully applied in different blue ice areas in Antarctica.
Articles in international scientific journals
Moore, J.C., A. Grinsted, T. Kekonen, and V. Pohjola, (2005). Separation of melting and environmental signals in an ice core with seasonal melt, Geophysical Research Letters doi:10.1029/2005GL023039
Jevrejeva, S., J.C. Moore , P. L. Woodworth and A. Grinsted, (2005). Influence of large scale atmospheric circulation on European sea level: results based on the wavelet transform method Tellus, 57A, 2, 183-193.
Kekonen,T. J.C Moore, P. Perämäki, R. Mulvaney, E. Isaksson, V. Pohjola and R. S. W. v.d. Wal, (2005). The 800 year long ion record from the Lomonosovfonna (Svalbard) ice core, Journal of Geophysical Research, 10.1029/2004JD005223
Grinsted, A. J. C. Moore, S. Jevrejeva (2004). Application of the cross wavelet transform and wavelet coherence to geophysical time series, Nonlinear Processes in Geophysics, 11, 561-566.
Jevrejeva, S.,J.C. Moore and A. Grinsted, (2004). Oceanic and atmospheric transport of multi-year ENSO signatures to the polar regions. Geophysical Research Letters, 31, L24210, doi:10.1029/2004GL020871
Grinsted, A., J. C. Moore, V. Spikes, and A. Sinisalo (2003). Dating Antarctic Blue Ice Areas using a novel ice flow model. Geoph. Res. Lett. 30(19), 2005. (10.1029/2003GL017957).
Kekonen,T., P. Perämäki and J.C. Moore (2003). Comparison of analytical results for chloride, sulfate and nitrate obtained from adjacent ice core samples by two ion chromatographic methods, Journal of Environmental Monitoring, doi:10.1039/ B306621E
Kohler, J., J.C. Moore and E. Isaksson (2003). Comparison of modelled and observed responses of a glacier snowpack to ground-penetrating radar. Annals of Glaciology 37, 293-297.
W. D. Miners and E. W. Wolff, J. C. Moore, R. Jacobel and L. Hempel (2002). Modeling the radio echo reflections inside the ice sheet at Summit, Greenland, Journal of Geophysical Research, 10.1029/2001JB000535
D. Rippin, I. Willis, N. Arnold, A. Hodson, J.C. Moore, J. Kohler and H. Björnsson (2003). Changes in geometry and subglacial drainage of Midre Lovénbreen, Svalbard, determined from Digital Elevation Models. Earth Surface Processes and Landforms 28 (3), 273-298.
Sinisalo, A., A. Grinsted, J. Moore, E. Kärkäs ja R. Petterson (2003). Snow accumulation studies in Antarctica with ground penetrating radar using 50, 100 and 800 MHz antenna frequencies. Ann. Glac. 37. , p. 194-198.
Sinisalo, A., J. Moore, R. van de Wal, R. Bintanja and S. Jonsson (2003). A 14-year mass balance record of a blue ice area in Antarctica. Ann. Glac. 37, p. 213-218.
Sinisalo, A, A. Grinsted and J. C. Moore. Scharffenbergbotnen blue ice area dynamics. Annals of Glaciology 39.
Senior scientist John Moore
Arctic Centre, University of Lapland