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Overturning of the Antarctic Slope Front and glacial melting along the coast of Dronning
Maud Land
Ole Anders NøstMartin Biuw, Christian Lydersen, Kit Kovacs, Qin Zhou
and Vigdis Tverberg
Norwegian Polar Institute
Elephant seals with CTD
The data
More than 1500 profiles within 100km of the coast/ice front
The colors separate the different seals.
The slope front and coastal current
Thermocline Depth
In this work we study the hydrographic conditions in the cold coastal waters above the thermocline.
All data within 100km of the coast
Daily averaged profiles plotted against time
Monthly TS diagrams
Red line:
Mixing with WDW
Blue line:
Melting/
Freezing
(Gade line)
Glacial melting:
Cold source waters and small salinity changes
October TS-plot
The development of salinity with time in the waters above the thermocline in a distance W=10km from the ice front/coast
S – Depth averaged salinity
SS – Surface salinity
SW - Near bottom salinity
Wind and surface heat fluxes calculated using NCEP and AMSR-E
sea ice consentration
Salinity as a result of
Surface and bottom Ekman flow.
wse SS
WD
V
dt
dS
Observations
Model
Q
HL
SQSS
WD
V
dt
dSws
e
Salinity as a result of
Surface and bottom Ekman flow.
Sea ice formation
Observations
Model
Q
HL
SQSS
WD
V
dt
dSws
e
SSWD
Vw
Salinity as a result of
Surface and bottom Ekman flow.
Sea ice formation
Overturning of the ASF
Glacial melting
• 2000 km coastline, 100000km2 ice shelves• 1.5 Sv overturning with temperature 0.2oC above
freezing.• Gives a melting of 1.4 m/year
Conclusions
• Hydrographic characteristics of the coastal current are given by a mix of surface water blown onshore and upwelled WDW. These are strongly mixed before interacting with ice shelves.
• Low salinities are caused by summer meltwater blown onshore by the westward winds. Glacial melting has little influence on salinity in the coastal current.
• Salinity increase during winter is mainly caused by overturning of the ASF, not sea ice formation.
• The strong overturning of the ASF provides enough heat to melt ~1m/year from the base of the ice shelves.