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.