The extent and duration of surface melting on the Antarctic ice shelve
s and margins of the Antarctic ice sheet are derived from satellite pa
ssive-microwave data for 1978-87. The occurrence of surface melting in
daily maps of T-b is indicated by a marked increase in microwave brig
htness temperature (T-b), which is caused by moisture in the near-surf
ace firn. T-b increases of more than 30 deg above the annual-mean T-b
are chosen to indicate melting. Most Antarctic surface melting occurs
during December and January. The observed melting is correlated with r
egional air temperatures, but some melt patterns also appear to be rel
ated to katabatic-wind effects. The correlations suggest that the surf
ace melting in Antarctica increases about 3.5 x 10(6) d km(2) per degr
ee of summer temperature increase. The surface-melt index (duration ti
mes area of melting) calculated for Antarctica is 24 x 10(6) d km(2),
averaged over nine summers. The observed inter-annual and regional var
iability is large. Surface melting was most extensive during the 1982/
83 summer (36 x 10(6) d km(2)) and least extensive during the 1985/86
summer (15 x 10(6) d km(2)). The data indicate a decline in surface me
lting over the 9 years, but meaningful inferences regarding trends in
surface melting are precluded by the large inter-annual variability.