Ice-atmosphere interactions during sea-ice advance and retreat in the

Western Antarctic Peninsula regionS. E. Stammerjohn, M. R. Drinkwater,

R. C. Smith, and X. LiuPresented by Brad Goodwin

Atmospheric Science Graduate Student

Sea-IceForms when surface

temperature drops below 29° FSalt excluded from ice, but still

saltier than land iceSea water becomes saltier and

denser, important for circulationTypically 1-6 feet thick around

AntarcticaChanges albedo and acts as an

insulator between ocean and atmosphere

Sea-Ice DynamicsChanges in position of

ice front with timeAtmospheric dynamics

or thermodynamics?How do ice-atmosphere

interactions respond to large scale atmospheric circulation patterns?

Western Antarctic PeninsulaCold, dry

continental air to the south

Warm, moist maritime air to the north

Data and MethodsUse satellite data and track extent as well as

motion of sea iceMeteorological data from two stations as well

as NCEP/NCAR Reanalysis dataDetermine opening, closing, and flux through

gatesDo not take into account tidal motion (short

time scale), only integrated 24-hour motion

Sea-Ice Extent

Sea-Ice Extent

Two Events – 1990 and 19921990 – 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 DriftFour 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 DataCold 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 RetreatJuly 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

TeleconnectionsSea-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 ConclusionsAtmospheric dynamics drive

sea-ice edge anomaliesAnnual 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 DirectionsNeed 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