Surface Heat Budgets in the Ross and Weddell Seas and Global Climate Variability

The monthly mean surface heat budgets, over last fifty years, in the Ross and Weddell Seas have been estimated using meteorological parameters provided by the ECMWF and sea ice information from SSM/I data and SIT (sea ice thickness) algorithm. The areas show opposite variations before 1998 and synchronous behaviour after 1999. This may be explained by the global climate variability expressed by ENSO, SAM and wavenumber-3 pattern or by combination among them. Also ACW could be involved. The interaction among these signals can imply a different behaviour of surface heat budgets in the two areas. Our results show that circumpolar SLP and SST signals exhibit coherent components on interannual whereas covarying significant energy between SAM and ENSO variability is observed. This implies that SAM and ENSO modes play a superimposed role interfering constructively or destructively on interannual scale. Furthermore, the hovmoller diagrams for interannual SLP anomalies exhibits two stronger ACW cycles around 1982-1991. Before 1982 and after 1991 the absence of ACW seems to be related to the dominant signature of SAM in modulating circumpolar variability. Also CEOF analysis show that the SAM has assumed a leading role between 1972-81 and 1991-2000 determining no ACW events. Starting from 2003 until present a wavenumber-3 pattern could have played a role in continuing the phase relationship between heat fluxes in the two Antarctic sectors.