Publication Date:
2021-05-10
Description:
We present biogenic opal flux records from two deep-sea sites in the Scotia Sea (MD07-
3133 and MD07-3134) at decadal-scale resolution, covering the last glacial cycle. In addition to
conventional and time-consuming biogenic opal measuring methods, we introduce new biogenic
opal estimation methods derived from sediment colour b*, wet bulk density, Si/Ti-count ratio
and Fourier transform infrared spectroscopy (FTIRS). All methods capture the biogenic opal
amplitude; however, FTIRS–a novel method for marine sediment – yields the most reliable
results. 230Th normalization data show strong differences in sediment focusing with intensified
sediment focusing during glacial times. At MD07-3134 230Th normalized biogenic opal fluxes
vary between 0.2 and 2.5 g cm22 kyr21. Our biogenic opal flux records indicate bioproductivity
changes in the Southern Ocean, strongly influenced by sea ice distribution and also summer sea
surface temperature changes. South of the Antarctic Polar Front, lowest bioproductivity occurred
during the Last Glacial Maximum when upwelling of mid-depth water was reduced and sea ice
cover intensified. Around 17 ka, bioproductivity increased abruptly, corresponding to rising atmospheric
CO2 and decreasing seasonal sea ice coverage.
Type:
Book chapter
,
NonPeerReviewed
Format:
text
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