TITLE:     Palmer LTER: Heat budgets and implications for circulation on the
           continental shelf west of the Antarctic Peninsula
AUTHOR     JM Klinck, RC Smith
PAGE:      152 of SCAR SIXTH BIOLOGY SYMPOSIUM, Antarctic Communities: Species,
           Structure and Survival 
ABSTRACT:  The seasonal change in heat content of continental shelf waters west
of the Antarctic Peninsula was estimated from temperature profiles obtained at
hydrographic stations during several cruises conducted as part of the Palmer
Long-Term Ecological Research program.  The spring to summer (November to
January) heat change is about 250 W m-2.  The cloud-free solar radiation for
this time is 140 W m-2, which is not sufficient to produce the observed
heating, especially since the heat loss due to cloud-free IR radiation from
the surface is about 100 W m-2.  Temperature measurements made in March and
April 1993 show that the temperature at 400 m decreased shoreward by 1.0
degrees C over 200 km (averaged alongshelf).  Similarly, the temperature
decreased to the north (averaged across shelf) by about 1.0 degrees C.  The
water offshore of the shelf break at 400 m is warmer than any water observed
on the shelf.  Temperature observations taken during the winter (August to
September 1993) have a similar pattern of lower temperatures to the north and
onshore.  This general pattern is consistent with an onshore and northward
alongshelf flow of the warmer offshore water.  The heat supplied by the
offshore water is used to warm the cold water produced during the previous
winter.  Upward vertical diffusion of heat into the surface layer can be
estimated to be 90 W m-2, using a moderately low diffusivity of 0.001 m2s-1.
Horizontal advection of heat through the water below the winter mixed layer
(temperature minimum layer) can be estimated to be 300 W m-2, assuming an
average across-shelf velocity of 0.01 ms-1 and an across-shelf temperature
difference of 0.4 degrees C.  The implication of these heat flux estimates is
that strictly vertical processes cannot account for the observed temperature
changes and there must be an import of heat.  The only source of warm water is
offshore, so there must be a general onshore flow of this water.  The decrease
in temperature alongshelf indicates that most of the onshore flow occurs at
the southern end of the shelf.  This influx of heat may explain the relatively
ice-free conditions observed west of the Antarctic Peninsula as compared to
the Weddell Sea to the east.