Combined satellite- and ULS-derived sea-ice flux in the Weddell Sea

Several years of daily microwave satellite ice-drift are combined with moored Upward Looking Sonar (ULS) ice-drafts into an ice volume flux record at points along a flux gate across the Weddell Sea, Antarctica. Monthly ice transport varies at the mooring locations from a maximum export of 0.4 m s near Joinville Island to -0.4 ms imported along the Fimbul and Riiser Larsen ice shelf margins. Winter peaks are observed at each end of the flux gate, where high concentrations of deformed ice are advected in and out of the basin along the coastline. The central gyre in contrast exhibits negligible seasonality and much smaller volume transports. Results indicate that gyre dynamics dominate net ice volume flux by controlling deformation and advection. During the period of overlapping ULS operation, the mean monthly integrated ice export west of the gyre center is 59 x 10 m s, and the import in the East Wind Drift is -17 x 10 m s. ULS data are compared with ERS satellite radar image pixel values to obtain an empirical relationship between ice thickness and the rate of change of backscatter with incidence angle. Resulting proxy ice-thickness data are combined with SSM/Iderived ice velocities to obtain seasonally varying estimates of net ice volume flux from 199298. Significant interannual variability is observed in ice volume flux expressed as freshwater transport. A maximum of 0.054 Sv is observed in 1992 with a minimum of 0.015 Sv in spring 1996. A six-year mean transport of 0.032 Sv is observed. Maximum seasonal ice export occurs in July 1992 with a minimum in November 1996. The ten-year mean area flux is 30 x 10 m s . Interannual variations in net volume flux closely follow variations in area flux with summer minima in 1990/91 and 1996/97. Maximum area transport occurs in 1991, and although this predates the ERS-1 scatterometer data, ice thickness estimates by Harms et al. confirm 1991 as a decadal peak in net integrated freshwater transport.