AGU journal highlights -- Aug. 1, 2007

Title: L-band microwave observations over land surface using a two-dimensional synthetic aperture radiometer

Authors: Dongryeol Ryu, Thomas J. Jackson, and Rajat Bindlish: Agricultural Research Service, Hydrology and Remote Sensing Laboratory, U.S. Department of Agriculture, Beltsville, Maryland, U.S.A.;

David M. Le Vine: Instrument Science Branch, NASA Goddard Space Flight Center, Greenbelt, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030098, 2007

12. North Atlantic climate and deep-ocean flow speed

In the Greenland, Iceland and Norwegian Seas, density and temperature differences cause cold, salty water to sink. Part of these dense water masses flow across the submarine sill between Iceland and Scotland. They are called Iceland-Scotland Overflow Water (ISOW) and contribute to North Atlantic Deep Water, a current that hugs the seafloor as it traces a path around Africa before joining deep waters surrounding Antarctica and later upwelling in the Pacific Ocean. Water returns to the northern Atlantic through a series of surface currents; this global ocean conveyor regulates climate by redistributing heat across the world's oceans. Using a sediment core from the subpolar North Atlantic, Boessenkool et al. study variations in the flow speed of ISOW over the past 230 years. They find that deep flow speeds of ISOW are coupled with the North Atlantic Oscillation (NAO), a climate mode that shifts the pathway and strength of Atlantic storms and depressions across Europe, with more vigorous ISOW flow when these storm tracks were over southern Europe and less vigorous ISOW flow when storm tracks were over northern Europe.

Title: North Atlantic climate and deep-ocean flow speed changes during the last 230 years

Authors: K. P. Boessenkool and I. R Hall: School of Earth, Ocean and Planetary Sciences, Cardiff University, Cardiff, U.K.;

H. Elderfield: Department of Earth Sciences, University of Cambridge, Cambridge, U.K.;

I. Yashayaev: Bedford Institute of Oceanography, Fisheries and Oceans Canada, Dartmouth, Nova Scotia, Canada.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030285, 2007

13. Comparing polar mesosphere summer echoes

Polar mesosphere summer echoes are strong signal power enhancements at very high radar frequencies that occur between about 80 kilometers (50 miles) and 95 kilometers (59 miles) in altitude at polar latitudes during summer. To determine whether the polar atmospheres between the Northern and Southern hemispheres are different, Latteck et al. compare continuous measurements of such echoes collected at Andenes, Norway, during the boreal summer of 2004 and Davis, Antarctica, during the austral summer of 2004-2005. They found that echoes observed at Davis are less reflective and reach maximum heights about 1 kilometer (0.6 miles) higher than those in the Northern Hemisphere. Further, polar mesosphere summer echoes occurred less frequently but with greater variability above Davis. Although both echo seasons started around the same time, the duration of the Davis season was about 9 days shorter than that at Andenes. Because such echoes are thought to provide information on middle atmosphere temperatures, the authors expect that continued research on this topic will help scientists understand climate patterns at the pole.