Measurements of the Surface Energy Budget on Multi-Year Ice at SHEBA

Measurements at the SHEBA Atmospheric Surface Flux Group (ASFG) tower site from October 1997 to September 1998 are used to describe the annual cycle of the surface energy budget. The SHEBA surface energy budget calculation is unique in its nearly exclusive use of observed rather than derived values. The magnitude of the net observed surface energy surplus at SHEBA was consistent with the observed surface ice and snow melt, and was in reasonable agreement with most previous estimates of the net annual surface energy budget over Arctic pack ice. However, the partitioning of the various components of the surface energy budget differed in the SHEBA data. The SHEBA site had unusually large incoming longwave radiation in March and April, giving a larger annual mean. The site also had substantially less incoming solar radiation than in previous estimates during most months. The observed magnitudes of the sensible and latent heat fluxes at SHEBA were smaller than previous climatological estimates, as were the conductive flux estimates at this site. Improvements to the conductive flux estimates and minor adjustments to other budget terms can be obtained using measurements and comparisons from other sites near the SHEBA ice camp. Such corrections, however, are unlikely to substantially alter the relative magnitudes of the terms in the SHEBA budget presented here but are necessary to assess reasons for the net thinning of the ice observed during SHEBA. Though the mean annual surface energy budget is the focus of the presentation, we emphasize that the mean budget consists of large and frequent variations in all surface energy budget terms. These variations appear to be associated with synoptic or mesoscale atmospheric disturbances.