Post-glacial seasonal diatom record of the Mertz Glacier Polynya, East Antarctica

Glacial ice and atmospheric forcing on the Mertz Glacier Polynya over the past 250 years

“…Increasing zonal wind circulation poleward may have contributed to accelerate the westward flowing Antarctic Slope Current, the southern branch of the Australian Antarctic Basin cyclonic circulation 51,52 , thus favouring the inflow of CDW through nonlinear momentum advection onto the shelf trough. Recent observations suggest that a weaker and more zonal circulation promote uplift and enhanced onshore intrusion of CDW 45 , and studies attributed an increased abundance of terrigenous particles in the sediments to enhanced melting of both continental and sea ice during periods of increased advection of warm CDW onto the shelf [17][18][19]53 . The high terrigenous content recorded in CB2010 since 1960 (Fig.…”

“…In the literature, variations in Ti content are largely used to infer past changes in terrigenous supply to the ocean 17 . Microfabric analysis of sediment in the Mertz-Ninnis and Adélie troughs show that both terrigenous content and Ti content are low in spring laminae and increase over the growing season (when open water diatoms dominate the siliceous assemblage) and during which the summer glacial melting is high 17,53,66 . Indeed, in Antarctic coastal areas, delivery of terrigenous particles is possible via several dominant modes as meltwater discharge, ice rafting, runoff from outlet glaciers and aeolian transport, although this latter source is considered negligible in coastal East Antarctic regions [17][18][19] .…”

A study of the diatom-dominated microplankton summer assemblages in coastal waters from Terre Adélie to the Mertz Glacier, East Antarctica (139°E–145°E)

“…or Nitzschia spp. Cores taken from the sediment near the Mertz Glacier showed abundant frustules from Fragilariopsis species, making this group the dominant diatom in recent times (Maddison et al 2006).…”

“…This zone was characterised by average to high Chl a concentrations (0.68 ± 0.14 lg l -1 at 5 m), high diatom diversity (H 0 = 0.85 ± 0.08) and average abundances (3,317 ± 2,790 cells l -1 at 5 m), and dominance of predominantly larger species such as Corethron pennatum and Rhizosolenia spp. These species are typically associated with open ocean conditions Crosta et al 2005;Maddison et al 2006) and would thrive better in these mixed waters than the smaller pennate diatoms due to drag-inducing adaptations that reduce their sinking rate, such as long appendages (in the case of C. pennatum) or their needle-like morphology (for Rhizosolenia spp.). This zone is also where the highest abundances of silicoflagellates were found (maximum 460 cells l -1 ), being very rare in the other two zones.…”

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“…Based on accelerator mass spectrometry radiocarbon dates on a 50 m long sediment core, this drift has unusually high accumulation rates, as much as 20-21 m/k.y. Opal, Ti, and Ba time series show decadal to century variance suggestive of solar forcing and El Niño Southern Oscillation (ENSO) forcing Denis et al 2006;Leventer et al, 2006;Maddison et al, 2006;Costa et al, 2007).…”