This is the main conclusion of new study from the ICM and the NCSU that assessed sedimentary environments in the vicinity of the Antarctic Peninsula, a region where temperature increase is 3 times the world average.
A new study from the Institut de Ciències del Mar (ICM) and from the North Carolina State University (NCSU) revealed that diverse environmental conditions off both coasts of the Antarctic Peninsula produce varied and unexpected signals in the sedimentary record decoupled from the formation environment.
According to the authors of the study, published this month in the journal Geochimica et Cosmochimica Acta, this assessment sets a baseline for the analysis of ongoing sedimentary conditions in the study area.
As explained in the study, the Antarctic Peninsula creates a natural climatic gradient, which varies from dry and polar conditions off its eastern coast in the Weddell Sea, to a more humid and oceanic setting off its western coast, including the South Shetland Islands in the Drake Passage.
The narrow (~70km) and relatively high (>1000m) Antarctic Peninsula acts as a barrier to the Southern Hemisphere westerlies, which transport warm and moist southern Pacific Ocean air toward the Peninsula. To the east of it, winds are mostly southerly, following the peninsular orography, and transport cold dry air, developing an East–West low to high temperature gradient over the region. A complex interplay of atmospheric circulation, near-surface winds and sea ice variability further influence climate trends in the region.
These climatic differences are evident at the sea surface, with higher values in the extent of sea ice cover, primary production and chlorophyll-a concentration, occurring in the Weddell Sea than in the adjacent Bransfield Strait and Drake Passage. Water circulation generates environmental differences as well; cold dense water from the Weddell Sea flows into the Bransfield Strait, where it encounters warmer water with Bellingshausen Sea influence, producing a temperature gradient near the seabed, which goes from <-1.5ºC in the Weddell Sea to >1ºC in the Drake Passage.
Based on these differences, higher organic carbon and biogenic silica contents would be expected in Weddell Sea sediments relative to the counterparts in the Bransfield Strait and the Drake Passage. However, as the authors of the study explain, significantly higher organic matter contents were observed in Bransfield Strait sediments.
The study concludes that a proportionally higher exported biogenic silica flux (relative to the local primary production) and better preservation conditions of organic carbon (i.e., lower seabed temperature) may contribute to make the Bransfield Strait a region with comparatively higher biogenic matter accumulation rates than in its neighboring regions (i.e., northeastern Weddell Sea and the Drake Passage).
“Relatively high preservation efficiencies resulted from extensive lateral sediment focusing, cold bottom water temperatures, and relatively high biogenic silica and organic carbon production rates in the euphotic zone”, explains Dave DeMaster, Professor of Chemical Oceanography at the NCSU and co-author of the study.
From his part, the ICM researcher Enrique Isla, lead author of the study, states that “the research should help to produce more accurate paleo-reconstructions along with the sedimentary record to avoid overestimations related to primary production in the Bransfield Strait and underestimations of primary productivity in the northern shelf off the South Shetland Islands”.