[1] GODDARD INST SPACE STUDIES, NEW YORK, NY 10028 USA
[2] CEA, DSM, CE SACLAY, MODELISAT CLIMAT & ENVIRONNEMENT LAB, F-91191 GIF SUR YVETTE, FRANCE
[3] CNRS, GLACIOL & GEOPHYS ENVIRONNEMENT LAB, F-38402 ST MARTIN DHERES, FRANCE
[4] NASA, GODDARD SPACE FLIGHT CTR, HYDROL SCI BRANCH, GREENBELT, MD 20904 USA
[5] COLUMBIA UNIV, LAMONT DOHERTY GEOL OBSERV, PALISADES, NY 10964 USA
[6] COLUMBIA UNIV, DEPT GEOL SCI, NEW YORK, NY 10025 USA