ROSETTA-Ice — Ross Ice Shelf, Antarctica Completed

By Geology, Geophysics, and Geochemistry Science Center June 20, 2019

ROSETTA-Ice is a large, NSF-funded, multi-disciplinary and multi-institutional project with several major goals focused on the full ice shelf system of the Ross Ice Shelf that include the ice, underlying seafloor bathymetry, and ocean interaction. Methods include the first comprehensive LC-130-based airborne geophysical survey of the Ross Ice Shelf to measure ice thickness and accumulation (ice-penetrating radars), map the ice surface (LiDAR and surface imagery), and identify geology and depth of the Ross embayment below the ice shelf (gravimeters and magnetometer), as well as deployment of ocean profiler drifters along the shelf edge to profile temperature, salinity, and velocity.

The Ross Ice Shelf (RIS)

Ice Shelf Calving Front — Ross Ice Shelf calving front.(Credit: Bethany Burton, USGS. Public domain.)

The Ross Ice Shelf (RIS) region is a locus of significant interactions between its geotectonic setting, ice sheet, and ocean that have important ramifications across multiple disciplines. With an area of 487,000 km², roughly the size of France, RIS ranges in thickness from 1,200 m closest to the grounding line to less than 300 m closer to the calving front along the Ross Sea. The edge of the ice shelf along the Ross Sea rises by as much as 50 m above the water. The Ross Ice Shelf is currently close to steady state but geological records indicate that it can disintegrate rapidly, which would accelerate grounded ice loss from catchments equivalent to 11.6 m of global sea level rise, motivating a climate interest in the region.

Prominent features in the bed topography below the floating RIS are broad, steep-sided, bedrock plateaus at 100 to 350 m below sea level, that are transected by glacial troughs reaching depths of 700 m or more. Recent studies suggest that a change in the flux of ocean heat into the ocean cavities underlying ice shelves is the most likely trigger for rapid future ice sheet mass loss within the coming decades to centuries. On longer time scales, the RIS mass budget may also be sensitive to changes in surface mass balance and ice advection across the grounding line. The current understanding of the shelf ice thickness and seafloor bathymetry below RIS is based on the 1970’s Ross Ice Shelf Geophysical and Glaciological Survey (RIGGS), with about 100 data points on a roughly 55-km grid across the entire shelf.

ROSETTA-Ice Flight Plan Map location and airborne survey coverage. Colors north of the Ross Ice Shelf indicate seafloor bathymetry from Bedmap2 compilation. Figure 1b from Tinto and others, 2019, https://doi.org/10.1038/s41561-019-0370-2.

Goal of ROSETTA-Ice

The overarching goal of ROSETTA-Ice during the 2015-2017 field seasons is to address fundamental questions of the structure and stability of RIS within the geotectonic framework for the Ross Embayment by focusing on the following key objectives:

Acquire the first comprehensive high resolution airborne geophysical data over RIS to support ice, ocean, and geotectonic studies with 10-km and 55-km line and tie-line spacing, respectively.
Acquire key oceanographic measurements along front of RIS.
Digitize, re-analyze and make more widely available RIGGS seismic and related geophysical data.
Use airborne gravity data with RIGGS seismic constraints to improved models of seabed bathymetry for the Ross Embayment, including under RIS.
Use the new aeromagnetic and gravity data to advance our understanding of the geotectonic framework of the region.
Use airborne ice-penetrating radar, LiDAR, and imaging to map RIS thickness and ice draft, and constrain RIS structure including basal channels, accumulation history, distribution of crevasses and marine ice.
Improve models of ice/ocean interaction with improved morphology, bathymetry and hydrographic observations, and investigate sensitivity of the RIS to future climate states.

Ross Ice Shelf map and cross section — Ross Ice Shelf Tectonic Setting: a) A simplified tectonic map showing the position of the newly mapped tectonic boundary beneath the Ross Ice Shelf, within a generalized tectonic reconstruction of the Mesozoic convergent margin of the Gondwana supercontinent, and b) A geological–tectonic cross-section across the Ross Ice Shelf region. Figure 2 from Tinto and others, 2019, https://doi.org/10.1038/s41561-019-0370-2.

ROSETTA-Ice geophysical results — ROSETTA-Ice survey potential field results: a) the magnetic anomaly from ROSETTA-Ice within the context of the ADMAP compilation for the surrounding area; the ROSETTA-Ice (2015) magnetic anomaly is represented both in colour and profile amplitudes (black lines,. b) the free air gravity anomaly from ROSETTA-Ice (2015-2016), within the context of AntGG48 and Ross Sea gravity grids, and c) relative variation in density modelled from inversion of the gravity anomaly from ROSETTA-Ice and other sources where water depth is known. The white line shows the location of the boundary between the West and East Antarctic lithosphere. Figure 3 from Tinto and others, 2019, https://doi.org/10.1038/s41561-019-0370-2.(Public domain.)

The project partners include an integrated science and engineer airborne team from Lamont-Doherty Earth Observatory (LDEO), glaciologists from Scripps, geologists from Colorado College, oceanographers from Earth and Space Research, geophysicists from U.S. Geological Survey, gravimeter support from GNS Science and Dynamic Gravity Systems, and air support from the New York Air National Guard 109th Airlift Wing.