S. E. Stammerjohn, M. R. Drinkwater, R. C. Smith, and X. Liu Presented by Brad Goodwin Atmospheric Science Graduate Student

Sea-Ice Forms when surface temperature drops below 29° F Salt excluded from ice, but still saltier than land ice Sea water becomes saltier and denser, important for circulation Typically 1-6 feet thick around Antarctica Changes albedo and acts as an insulator between ocean and atmosphere

Sea-Ice Dynamics Changes in position of ice front with time Atmospheric dynamics or thermodynamics? How do ice-atmosphere interactions respond to large scale atmospheric circulation patterns?

Western Antarctic Peninsula Cold, dry continental air to the south Warm, moist maritime air to the north

Data and Methods Use satellite data and track extent as well as motion of sea ice Meteorological data from two stations as well as NCEP/NCAR Reanalysis data Determine opening, closing, and flux through gates Do not take into account tidal motion (short time scale), only integrated 24-hour motion

Sea-Ice Extent

Two Events – 1990 and – Late onset of sea-ice advance and late onset of sea-ice retreat 1992 – Early onset of sea-ice advance and early onset of sea-ice retreat

Four Days of Sea-Ice Drift Four consecutive days of sea level pressure, wind, and sea ice drift Red arrows added to show predominant direction of sea ice drift Rapid changes in drift direction with changes in wind direction and speed Also important for amount of open water detected

Comparison with Station Data Cold temperatures, light winds during sea-ice advance Warm temperatures, strong northerly winds during sea- ice retreat Largest day-to-day changes in extent and concentration were related to wind-driven sea-ice drift so…

The answer is…

Timing of Advance and Retreat July 1990 – northerly winds, CPT near ice- edge, ice-edge retreats August 1990 – CPT south of ice-edge, zonal winds, ice-edge recovers July 1992 – high pressure, southerly winds, ice-edge advances August 1992 – CPT near ice-edge, ice-edge retreats

Teleconnections Sea-ice west of the Antarctic Peninsula behaves differently than sea-ice in the rest of the southern hemisphere Position and strength of CPT important for determining timing and extent of ice-edge advance and retreat CPT influenced by the semi-annual oscillation (SAO) and El Nino-Southern Oscillation (ENSO) SAO is a twice a year contraction and expansion of the pressure trough around Antarctica Tropical Pacific is important for understanding sea-ice dynamics around Antarctica

Summary and Conclusions Atmospheric dynamics drive sea-ice edge anomalies Annual cycle in sea-ice edge is determined by the persistence and intensity of regional atmospheric circulation Changes in ice-edge over time are related to the amplitude and phase of the SAO (meridional temperature gradient) as influenced by ENSO and/or regional/global warming

Future Directions Need to better understand teleconnection relationships between the tropical Pacific and the Antarctic Peninsula region My research focuses on an ice core collected from the Antarctic Peninsula Evidence for relationship between accumulation on the AP and the Southern Annular Mode as well as ENSO Teleconnections related to sea-ice dynamics and accumulation may have similar sources These relationships need to be better understood