Relationship between magnetic susceptibility and sediment grain size since the last glacial period in the Southern Ocean off the northern Antarctic Peninsula – Linkages between the cryosphere and atmospheric circulation

Abstract. Abrupt millennial–scale climate change events of the last deglaciation (i.e., Heinrich Stadial 1 and the Younger Dryas) were accompanied by marked increases in atmospheric CO2 presumably originated by outgassing from the Southern Ocean. However, information on the preceding Heinrich Stadials during the last glacial period is scarce. Here we present stable carbon isotopic data (δ13C) from two species of planktonic foraminifera from the western South Atlantic that reveal major decreases (up to 1 ‰) during Heinrich Stadials 3 and 2. These δ13C decreases are most likely related to millennial–scale periods of intensification in Southern Ocean deep water ventilation presumably associated with a weak Atlantic meridional overturning circulation. After reaching the upper water column of the Southern Ocean, the δ13C depletion would be transferred equatorward via central and thermocline waters. Together with other lines of evidence, our data are consistent with the hypothesis that the CO2 added to the atmosphere during abrupt millennial–scale climate change events during the last glacial period also originated in the ocean and reached the atmosphere by outgassing from the Southern Ocean. The temporal evolution of δ13C during Heinrich Stadials in our records is characterized by two relative minima separated by a relative maximum. This “w–structure” is also found in North Atlantic and South American records, giving us confidence that such structure is a pervasive feature of Heinrich Stadial 2 and, possibly, also Heinrich Stadial 3.

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Fragilariopsis kerguelensis size variability from the Indian subtropical Southern Ocean over the last 42 000 years

Antarctic Science ◽

10.1017/s095410201600050x ◽

2016 ◽

Vol 29 (2) ◽

pp. 139-146 ◽

Cited By ~ 5

Author(s):

Sunil Kumar Shukla ◽

Xavier Crosta

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Glacial Period ◽

Last Glacial Period ◽

Subtropical Zone ◽

The Holocene ◽

Last Glacial ◽

Size Variability ◽

The Last Glacial ◽

Valve Area

AbstractIn the open Southern Ocean (SO), both modern and past size changes of the diatom Fragilariopsis kerguelensis appear to be strongly controlled by iron availability. Conversely, sea surface temperatures (SST) and sea ice seasonal dynamics take over in the seasonal sea-ice zone where iron is not limiting. No information exists on F. kerguelensis biometry from the subtropical SO, on the other extreme of the thermal and nutrient gradients. We present here new data on mean valve area of F. kerguelensis (FkergArea) from a sediment core covering the last ~42 cal kyrs from the southern Subtropical Front (SSTF) of the Indian sector of the SO, where iron and silica stocks are thought to have been consistently low over this period. Our results suggest that larger F. kerguelensis valves occurred during the Last Glacial period, and declined during the Holocene period. These findings indicate that more favourable SST, within the F. kerguelensis ecological range, during the Last Glacial period may have enabled F. kerguelensis to make better use of the low silica stocks prevailing in the subtropical zone leading to larger valves. Conversely, declining FkergArea during the deglacial and the Holocene periods may have been a result of higher SST which hampered the utilization of silica.

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Chronology and provenance of last-glacial (peoria) loess in western iowa and paleoclimatic implications

Quaternary Research ◽

10.1016/j.yqres.2013.06.006 ◽

2013 ◽

Vol 80 (3) ◽

pp. 468-481 ◽

Cited By ~ 39

Author(s):

Daniel R. Muhs ◽

E. Arthur Bettis III ◽

Helen M. Roberts ◽

Stephen S. Harlan ◽

James B. Paces ◽

...

Keyword(s):

Grain Size ◽

Missouri River ◽

Optically Stimulated Luminescence ◽

Laurentide Ice Sheet ◽

Glacial Period ◽

Accumulation Rates ◽

Last Glacial Period ◽

Last Glacial ◽

The Earth ◽

The Last Glacial

Geologic archives show that the Earth was dustier during the last glacial period. One model suggests that increased gustiness (stronger, more frequent winds) enhanced dustiness. We tested this at Loveland, Iowa, one of the thickest deposits of last-glacial-age (Peoria) loess in the world. Based on K/Rb and Ba/Rb, loess was derived not only from glaciogenic sources of the Missouri River, but also distal loess from non-glacial sources in Nebraska. Optically stimulated luminescence (OSL) ages provide the first detailed chronology of Peoria Loess at Loveland. Deposition began after ~ 27 ka and continued until ~ 17 ka. OSL ages also indicate that mass accumulation rates (MARs) of loess were not constant. MARs were highest and grain size was coarsest during the time of middle Peoria Loess accretion, ~ 23 ka, when ~ 10 m of loess accumulated in no more than ~ 2000 yr and possibly much less. The timing of coarsest grain size and highest MAR, indicating strongest winds, coincides with a summer-insolation minimum at high latitudes in North America and the maximum southward extent of the Laurentide ice sheet. These observations suggest that increased dustiness during the last glacial period was driven largely by enhanced gustiness, forced by a steepened meridional temperature gradient.

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