LARISSA

Marine and Quaternary Geosciences

(Domack, Leventer, Brachfeld, Ishman, Wellner, Balco)


The LARISSA Project represents an Earth Systems approach to describe and understand the basic physical and geological processes active in the Larsen embayment that a) contributed to the present phase of massive, rapid environmental change; b) are participating in that change as part of the coupled climate-ocean-ice system; and c) are fundamentally altered by these changes.  This requires a comprehensive, interdisciplinary approach that includes geological, glaciological, oceanographic, and biological data, all needed to fully characterize the major linkages and interactions between different parts of the system. As part of this effort, the Marine and Quaternary Geosciences component of the project will focus on addressing the following research questions:
 
(1) What does the stratigraphic record from prior to the Last Glacial Maximum reveal about the extent of the Larsen Ice Shelf under climate conditions of the penultimate interglacial (approximately ~125 ka) when global conditions of sea level and average climate were higher and warmer, respectively, than today?
   
  (2) What was the detailed configuration of the northern Antarctic Peninsula Ice Sheet (APIS) during the Last Glacial Maximum (LGM) and subsequent retreat?
   
  (3) Why has the Larsen B Ice Shelf been a stable component of the cryosphere through the Holocene epoch, while other ice shelves have apparently come and gone during periods of natural climate variability?
   
  (4) What controls the dynamics of ice-shelf grounding-line systems and what role does meltwater or oceanic processes play in their stability?
   
        
(5) What changes in sediment flux (both lithogenic and biogenic) accompany large scale ice shelf disintegration and post break up surge of tributary glaciers, and what is the temporal and spatial pattern of this pulse of sediment across the basin?
   


This will be accomplished through an integrated multi−disciplinary field program on the eastern Antarctic Peninsula margin including the Larsen Embayment of the western Weddell Sea shelf (Figure 1). The field program will include:

       
  • High-resolution seismic data acquisition, correlated to the seafloor morphology and sedimentologic facies of the region, to determine the history of past ice-sheet/shelf fluctuations (Figures 2 & 3).
 
  • Jumbo piston coring, kasten coring and deployment of instrumented moorings (Figure 1 & 2) to enable us to match sedimentary signatures to environmental processes, and then apply those interpretations down core, into the past. The Hektoria Basin record will allow us to look at long-term patterns in the LIS system.
 
  • Multibeam seafloor mapping, sediment coring, GPS and surface exposure dating (Figures 1, 2 & 3). A strategy of utilizing a combination of land based geomorphology/cosmogenic exposure dating correlated with marine stratigraphy and seafloor morphology/seafloor glacial features will provide constraints on ice thickness and paleo-extent of the LGM in the NW Weddell Sea.
 
 
A host of methods will be applied to sediment and sediment core samples to provide paleoenvironmental reconstructions from the marine record (Figure 4) that will be correlated to the ice core record collected from the Bruce Plateau as part of our coordinated proposal with Scambos and others (Figure 1).  These include:

         
  • Detailed radiogeochemistry (210Pb and 14C) analysis on mega cores and kasten cores coupled with sediment trap deployment to quantify the sediment regime.
 
  • Study of marine proxies: diatom assemblages, foraminiferal assemblages, sediment magnetic properties, sediment particle size, sediment physical properties and geochemistry, and biogeochemistry.