Delta progradation and offshore sedimentary lobes in the northern coast of the Brøgger Peninsula (Spitsberg, Svalbard)
Abstract
Arctic coastal areas: • faster and greater modifications than other coastlines (Overduin et al. 2014). • little known about the physical processes that control coastal high-latitudes and how they will evolve (Zagorski et al. 2013). - NW Spitsbergen: post-LIA retreating glaciers and destabilization of glacial landforms by climate change have released a substantial amount of sediment which is reworked by runoff and builts coastal sandur deltas (Mercier & Laffly, 2005). - Purpose: to understand the post-Little Ice Age sedimentary transfer in Kongsfjorden. Quantification of the coastal evolution from 1966 to 2014. Material and Methods: - Shoreline evolution: • 1966-1990: photo interpretation of aerial photographs from 1966, 1971, 1977,1990. • 2011-2014: dGPS data Reference line parallel to the coast with reference points every 50 m. Shoreline movements measured by calculation distance between reference points and each shoreline. Different metric error for each year of measurement. - Prodeltas evolution: • side scan sonar mosaics interpreted for 2009, 2011 and 2012. Results: Shoreline evolution from 1966 to 1990: • Coastal progradation trend. • Delta 3 was the most dynamic: mean of + 4.83 m/yr and max advance value of +86 m. • Total coastal progradation estimated at 78 889 m². - Shoreline evolution from 2011 to 2014: • Each delta prograded on their west side and is eroded on their east side. • Except for delta 3, progradation is higher than erosion. • Delta 1 experienced the strongest shoreline progradation with a mean of + 4.04 m/yr. - Prodeltas evolution from 2009 to 2012: • Prodelta (a) remained stable. • Extent increase of prodeltas (b) and (c): Prodelta (b): + 9000 m² = + 56 % Prodelta (c): + 30 000 m² = + 27 % • In 2012, the total surface of the prodeltas is estimated at 60 267 m² for prodelta (a), 24 270 m² for prodelta (b) and 135 498 m² for prodelta (c). Conclusion: Coastal progradation and prodeltas extent illustrate the substantial sedimentary input in the fjord. - This progradation coastal trend should continue until the run out of the sedimentary supply due to runoff.