Response of Arctic submarine continental slopes to global warming
Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
Final Report Abstract
The overarching goal of the project is to evaluate how the currently predicted increment in temperature may change the dynamics of the hydro-geological system and how that change may alter the stability of the slope of Arctic continental margins. For that we need to study the history of the buildup of the margin first, which is currently poorly known. I used seismic reflection data, multibeam bathymetry and existing core data from two marine campaigns from 2007 and 2008: SVAIS (The development of an Arctic ice streamdominated sedimentary system: The southern Svalbard continental margin) and EGLACOM (Evolution of a glacial Arctic continental margin: The southern Svalbard ice streamdominated sedimentary system). During seismic interpretation, the deepest sediment units and top of basement were poorly imaged, partially because the previous interest was focused on relatively shallow mass transport deposits (MTDs) that were obvious in the data and had attracted the investigations. To fully understand margin development, I reprocessed the seismic data, which brought several improvements, like the definition and morphology of the top of the basement, that facilitated defining the seismic units. This has permitted to map the full stratigraphy of the margins and create a first 3D model of distribution of sediment bodies. In addition, there was a serendipitous discovery, I discovered that some of the deep structures that were unclear in the original records most likely represent giant MTDs. Reprocessing improved the imaging of the deeper structure so dramatically that the complex internal geometry of a series of deep-seated MTD deposits was revealed. The new results provide an image of the deeper structures that supports that giant MTDs, previously unknown, occurred during the early phases of the development of the continental margin. The newly identified structures are located below reflector R5 (onset of Northern Hemisphere large-scale glaciation), corresponding to older sediment ages between 2.1- 2.7Ma. Thus, their origin may be related in some yet unknown causal relationship to climate or climate and tectonics. Previous work revealed Paleo-slides only above the Reflector R4A (younger than 1.3 Ma). These slides range in thickness from meters up to 150m, and in width from hundreds of meters to almost 50km, and runouts from tens of meters to 120km. The giant MTDs that I discovered here seem to be much larger and extend (as imaged on several lines) over 100s of kilometers with up to ~1km thick bodies. The stratigraphy model shows that these MTDs must have possibly happened during onset of the Northern Hemisphere Glaciation (NHG), when the Barents Sea Ice sheet advanced the shelf for the first time, Dimensions and inferred run out from internal structuration of these MTDs supports that they may have derived from the northeast of Svalbard coast running towards the southwest into the Norwegian Greenland Sea. They appear to have been stopped at the physical barrier of the Knipovich ridge. Further investigation of this new finding is underway to study the potential links to climate or tectonic processes. The new findings may affect current understanding on submarine mass wasting processes of glacial margins in general and of Svalbard. Clearly, general sizefrequency distributions along the slope need to be adjusted. More importantly, slope stability processes accompanying an onset of glaciation need to be better understood. There is a need to reexamine preconditioning and trigger mechanisms including loading, fluid pathways, and tectonics in the area, which cannot be explained by currently accepted models.
