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SUMMARY:Quantifying transport time and degradation of terrigenous organic 
 carbon across the East Siberian Arctic shelf - Lisa Bröder
DTSTART:20180309T140000Z
DTEND:20180309T150000Z
UID:TALK101932@talks.cam.ac.uk
CONTACT:Christine Lane
DESCRIPTION:Permafrost soils in the Arctic store large quantities of organ
 ic matter\, roughly twice the amount of carbon that was present in the atm
 osphere before the industrial revolution. This freeze-locked carbon pool i
 s susceptible to thawing caused by amplified global warming at high latitu
 des. The remobilization of old permafrost carbon facilitates its degradati
 on to carbon dioxide and methane\, thereby providing a positive feedback t
 o climate change.\n\nAccelerating coastal erosion in addition to projected
  rising river discharge with enhancing sediment loads are anticipated to t
 ransport increasing amounts of land-derived organic carbon (OC) to the Arc
 tic Ocean. On its shallow continental shelves\, this material may be remin
 eralized in the water column or in the sediments\, transported without bei
 ng altered off shelf towards the deep sea of the Arctic Interior or buried
  in marine sediments and hence sequestered from the contemporary carbon cy
 cle. The fate of terrigenous material in the marine environment\, though o
 ffering potentially important mechanisms to either strengthen or attenuate
  the permafrost-carbon climate feedback\, is so far insufficiently underst
 ood.\n\nWe have used sediments from the wide East Siberian Arctic Shelf\, 
 the world’s largest shelf-sea system\, to investigate some of the key pr
 ocesses for OC cycling. A range of bulk sediment properties\, carbon isoto
 pes and molecular markers were employed to elucidate the relative importan
 ce of different organic matter sources\, the role of cross-shelf transport
  and the relevance of degradation during transport and after burial.\n\nTh
 is talk focuses on how we can employ compound-specific radiocarbon analyse
 s of terrestrial biomarkers to determine cross-shelf transport times and q
 uantify degradation rates for terrigenous OC (terrOC). For the 600 km from
  the Lena River Delta to the Laptev Sea shelf edge our quantitative estima
 te resulted in 3600 ± 300 years. During transport\, terrOC was reduced by
  ~85%\, thus yielding a degradation rate constant of 2.4 ± 0.6 kyr-1. Hen
 ce\, terrOC degradation during cross-shelf transport constitutes a carbon 
 source to the atmosphere over millennial time. For the contemporary carbon
  cycle on the other hand\, slow terrOC degradation brings considerable att
 enuation of the decadal-centennial permafrost carbon-climate feedback caus
 ed by global warming.
LOCATION:Small Lecture Theatre\, Department of Geography\, Downing Site
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