TIDEx

Transantarctic Ice Deflection Experiment – Darwin Glacier (79°53′ S 159°00′ E)

Measuring tidal ice flexure in the grounding zone of an outlet glacier to constrain satellite-based modelling.

darwin

Quantifying the Antarctic contribution to global sea-level rise requires detailed knowledge about the amount of ice discharge from the continent to the ocean. To calculate this mass transport, the ice thickness along the Antarctic periphery is key information.  In order to cover the entire coastline the usage of satellites is inevitable, because ground measurements of ice thickness and melting beneath the ice surface are sparse. However, ice thickness distribution cannot be measured directly from satellites, so indirect space-borne remote sensing techniques are required.

Outlet glaciers like the Darwin flow from the Antarctic plateau into the Ross Sea. As the ice becomes afloat on the ocean, it is bending up and down by the tides. The resulting ice flexure  is in turn proportional to the ice thickness within the grounding zone. Our expedition provides information about their relationship which is a proper understanding about the physical principles behind tidal bending of ice – the so called ice rheology.

To understand the forces on glaciers associated with ocean tides and guide our interpretation of satellite data from grounding zones elsewhere. The Darwin Glacier grounding zone is largely blue ice providing a homogeneous ice column through which to calculate ice rheology (no complications caused by variable density & firn compaction). The glacier has a surface velocity of about 50 m/yr which is fast enough to give us reasonable confidence of similarity with other outlet glaciers (so that we can apply the knowledge gained elsewhere) but slow enough to avoid extensive surface crevassing making fieldwork difficult. This will involve setting up closely spaced tiltmeters and GPS receivers to record data over 1 tidal cycle (14 days). They will be set up when we arrive in the field and removed before we leave our study site. After they are set up we will take ground penetrating radar measurements to fill in gaps in existing data and look for ice thickness change since a previous campaign in 2008. We will also take phase-sensitive radar measurement of basal melting below the floating ice – the first measurements of ocean-induced melting at a Transantarctic Mountain glacier grounding line.

After arriving at Scott Base, which is the permanent presence of New Zealand Antarctic research, we will be travelling to the Darwin Glacier and stay on-site for almost one month. This expedition developed from a collaboration between the German Aerospace Center (DLR) and Gateway Antarctica. Its four members consist of Dr. Oli Marsh, Ekki Scheffler, Dana Floricioiu and me. After months of preparation, we will finally depart South. Follow us on another “life-changing experience”.

 

 

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