TITLE: Palmer LTER: CLIMATE VARIABILITY in the WEST ANTARCTIC PENINSULA REGION
AUTHOR: R.C.Smith, S.E.Stammerjohn, K.S. Baker
DATE: 31 Aug - 4 Sep 1998
PLACE: SCAR VII International Biology Symposium in New Zealand 


Raymond C. Smith, ICESS, University of California at Santa Barbara
Sharon E. Stammerjohn, ICESS, University of California at Santa Barbara
Karen S. Baker, SIO, University of California at San Diego

   In the Western Antarctic Peninsula (WAP) region sea ice and air
temperature variability are strongly linked and indicate over the last
half century a long-term warming and a coherency with the El
Nino/Southern Oscillation (ENSO) phenomenon (Smith et al.  1996).
The WAP region therefore appears to be an ideal area to study
ecological response to climate variability.  To this end, the Palmer
Long-Term Ecological Research project (Smith et al. 1995), which
focuses on the marine ecosystem in the WAP seasonal sea ice zone, has
as their central tenet that the seasonal and interannual variability of
sea ice affects all levels of the Antarctic marine ecosystem.  A set of
sea ice indexes have been developed to describe the interannual
fluctuations and high seasonality of sea ice (Smith et al. 1998).
These simplified ecological indicators quantify the timing and
magnitude of sea ice coverage on temporal and spatial scales relevant
to testing sea ice-ecosystem linkages.

   Surface air temperature records from several stations in the WAP
region show an along-peninsula temperature gradient, indicating the
sensitivity of this region to the contrasting influences of maritime
versus continental climate regimes.  The 54-year Faraday/Vernadsky air
temperature record (1944-97) (Jones and Limbert, 1987; Shanklin
personal communication) shows a strong warming trend of 4-5C in the
months of May to August and a smaller warming trend of 1.3 to 1.6C in
the months of January to March.  To date, detectable (>90% confidence)
decreasing trends in sea ice coverage are found only in summer for the
regions adjoining the southeast Pacific Ocean (ie., the WAP and greater
Bellingshausen and Amundsen regions), while increasing trends have been
detected in non-winter months for all other regions of the Southern
Ocean (Stammerjohn and Smith 1997).  In addition, the WAP and greater
Bellingshausen regions are the only Southern Ocean regions which show
long-term persistence in monthly anomalous sea ice coverage,
illustrated by the oscillation between several consecutive high ice
years followed by several consecutive low ice years (Stammerjohn and
Smith 1996).  This long term persistence appears to be related to the
quasi-periodic ENSO phenomenon.  For example, significant low and high
frequency coherence has been detected between Faraday/Vernadsky air
temperature and the Southern Oscillation Index (SOI), indicating a
strong interplay between the regional climates of equatorial and
southeastern Pacific (Smith et al. 1996).  Ongoing research is involved
in better understanding the climate controls influencing sea ice
variability and consequently the changes observed in the marine
ecosystem.

References

Jones P.D. and Limbert D.W.S. 1987. Carbon Dioxide Database.

Smith R.C., Baker K.S., Fraser W.R., Hofmann E.E., Karl D.M., Klinck
  J.M., Quetin L.B., Prezelin B.B., Ross R.M., Trivelpiece W.Z., Vernet
  M. 1995.

Smith R.C., Stammerjohn S.E., Baker K.S. 1996. Antarctic Research
  Series 70, 105-121.

Stammerjohn S.E., Smith R.C. 1996. Antarctic Research Series 70,
  81-104.

Stammerjohn S.E., Smith R.C. 1997. Climatic Change 37, 617-639.

Smith R.C., Baker K.S., Stammerjohn S.E. 1998. BioScience 48, 83-93.