Climate mediated size variability of diatom Fragilariopsis kerguelensis in the Southern Ocean

Shukla, Sunil Kumar; Crosta, Xavier; Cortese, Giuseppe; Nayak, G. N.

doi:10.1016/j.quascirev.2013.03.005

Cited by 26 publications

(48 citation statements)

References 60 publications

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“…As per the study, variations in circumpolar upwelling along with nutrient inputs from Antarctic Peninsula have exerted a strong control on F. kerguelensis valve size in the Atlantic and Indian sector of the SO. Size records from the Atlantic sector demonstrate larger valve sizes of F. kerguelensis during the Last Glacial Period, which is possibly related to greater iron availability through wider sea-ice coverage and higher eolian dust input (Shukla et al, 2013). But the scenario is different in the Indian sector (Fig.…”

Section: Diatoms For Deciphering the Southern Ocean Paleoclimatementioning

confidence: 96%

Section: Abhilash Nair and Rahul Mohanmentioning

confidence: 99%

“…Changes in the valve size of F. kerguelensis in deep-sea sediment cores from the Indian and the Atlantic sectors of SO were recently used to infer changes in diatom productivity, physiology and environmental conditions (Shukla et al, 2013;Nair et al, 2015). Shukla et al (2013) suggested that variations in circum-polar upwelling were the main controlling factor in opal production during the last 20,000 years. It was also hypothesized that high nutrient input from the Antarctic Peninsula during the last deglaciation may have exerted a strong control on F. kerguelensis valve size and opal export in the Atlantic sector of the Southern Ocean (Shukla et al, 2013).…”

Section: Abhilash Nair and Rahul Mohanmentioning

confidence: 99%

“…Shukla et al (2013) suggested that variations in circum-polar upwelling were the main controlling factor in opal production during the last 20,000 years. It was also hypothesized that high nutrient input from the Antarctic Peninsula during the last deglaciation may have exerted a strong control on F. kerguelensis valve size and opal export in the Atlantic sector of the Southern Ocean (Shukla et al, 2013).…”

Section: Abhilash Nair and Rahul Mohanmentioning

confidence: 99%

“…Diatoms have been studied in consideration with past climate reconstruction and oceanographic settings from Southern Ocean.One such study by Shukla et al, (2013) involves the morphometric analysis of abundant diatom species (F. kerguelensis) in the SO (Fig. 1).…”

Section: Diatoms For Deciphering the Southern Ocean Paleoclimatementioning

confidence: 99%

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Paleoclimatic Signals from the Proxy Records of the Southern Ocean: A Review

Nair

Mohan

2017

Proceedings of the Indian National Science Academy

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Antarctic sea-ice extent and oceanic frontal systems are of primary importance to the marine biota since their marked meridional gradients in physical and chemical properties strongly regulate the phytoplankton contribution to primary productivity.Antarctic sea ice extent along with the Southern Ocean (SO) biological productivity varied considerably during glacial-interglacial periods, and both are known to have played a considerable role in regulating atmospheric CO 2 variations in the past. In the present review paper, we seek to understand the past latitudinal variability of the Southern Ocean frontal systems and Antarctic sea-ice extent based on a multi-proxy approach. The first aspect of this paper concentrates on the diatom based reconstructions of paleo sea-ice and hydrographic changes in the Southern Ocean and its impact on diatom sizes and productivity. Secondly, emphasis would be placed on the studies based on the morphology and isotopic composition of foraminifera and its paleoceanographic implication. The foraminifera shell preserved in the sediments provide unparalleled archives of morphological change, faunal variations, and habitat characteristics as a result of hydrographic changes. To sum up, the advantage of a mulitproxy approach including the magnetic, geochemical and sedimentological parameters have been discussed in understanding the Southern Ocean paleoclimate.

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Section: Diatoms For Deciphering the Southern Ocean Paleoclimatementioning

confidence: 96%

Section: Abhilash Nair and Rahul Mohanmentioning

confidence: 99%

Section: Abhilash Nair and Rahul Mohanmentioning

confidence: 99%

Section: Abhilash Nair and Rahul Mohanmentioning

confidence: 99%

Section: Diatoms For Deciphering the Southern Ocean Paleoclimatementioning

confidence: 99%

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Paleoclimatic Signals from the Proxy Records of the Southern Ocean: A Review

Nair

Mohan

2017

Proceedings of the Indian National Science Academy

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Glacial‐interglacial variability in diatom abundance and valve size: Implications for Southern Ocean paleoceanography

Nair

Mohan

Manoj³

et al. 2015

Paleoceanography

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Antarctic sea ice extent along with Southern Ocean biological productivity varied considerably during glacial-interglacial periods, and both are known to have played a considerable role in regulating atmospheric CO 2 variations in the past. Here we present data on diatom absolute abundance (valves/g of sediment) and size over the past~42 ka B.P. and how they link to glacial-interglacial changes in Antarctic sea ice extent, Southern Ocean frontal systems, and aeolian dust flux. Our records of sea ice and permanent open ocean zone diatom abundances suggest a shift in the Antarctic winter sea ice limit and Polar Front respectively up to the modern-day Polar Frontal Zone during marine isotopic stages (MIS) 2 and late MIS 3. In addition to glacial shifts in the Polar Front, diatom assemblages also recorded a plausible northward shifts in Polar Front during few intervals of MIS 1. Glacial periods north of the Polar Front in the Indian sector of the Southern Ocean were characterized by higher total diatom abundance, larger Fragilariopsis kerguelensis apical length, and Thalassiosira lentiginosa radius. This is probably a consequence of (1) a northward expansion of the opal belt, a region characterized by high production and export of biogenic silica; (2) an increase in terrigenous input, via erosion of Crozet Islands; and (3) the alleviation of iron deficit by high input of Fe-bearing dust. The larger and highly silicified diatoms such as F. kerguelensis and T. lentiginosa may have mainly contributed in transporting biogenic silica and organic carbon to the seabed for the last 42 ka, in the northern Polar Frontal Zone of the Indian sector of the Southern Ocean.

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The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle

et al. 2014

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The Southern Ocean plays a critical role in the air-sea CO 2 balance through biological and physical mechanisms. Vertical supply of deep waters returns nutrients and CO 2 to the surface and stimulates phytoplankton growth. Photosynthesis in the Southern Ocean is limited by iron and only a fraction of the carbon and nutrients that return to the surface are consumed for potential sequestration in the deep sea. Here we present the most spatially extensive data set of silicon and nitrogen isotope measurements from diatom frustules to date to examine the controls on nutrient drawdown during the last glacial period and across the glacial termination in both the Antarctic and Subantarctic zones. The new data confirm existing views that differing silicon and nitrate consumption patterns in the Antarctic zone are likely the result, at least in part, of iron addition during the last glacial maximum (LGM). However, earlier in the glacial, a more coordinated response in the two proxy records, with both reflecting enhanced consumption during episodes of increased iron accumulation and export production, implies a different system response than observed for the LGM. A collapse of the expected equatorward gradient in silicon isotope values and contraction of the nitrogen isotope gradient during the deglaciation suggests that nutrient supply increased not only in the Antarctic Zone, but also in the Subantarctic, perhaps due to enhanced deep mixing locally. Enhanced deep water ventilation across the Southern Ocean likely increased the nutrient content of mode waters during the deglaciation.

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Climate mediated size variability of diatom Fragilariopsis kerguelensis in the Southern Ocean

Cited by 26 publications

References 60 publications

Paleoclimatic Signals from the Proxy Records of the Southern Ocean: A Review

Paleoclimatic Signals from the Proxy Records of the Southern Ocean: A Review

Glacial‐interglacial variability in diatom abundance and valve size: Implications for Southern Ocean paleoceanography

The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle

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