Eucampia Index as an indicator of the Late Pleistocene oscillations of the winter sea-ice extent at the ODP Leg 119 Site 745B at the Kerguelen Plateau

Abstract

A new paleoenvironmental proxy, Eucampia Index, was used to trace the Late Pleistocene oscillations of winter ice extent at ODP Leg 119, Site 745B (59° 35 .71' S and 85' 51 .60' E) on the Kerguelen Plateau . The index is calculated as the ratio of winter terminal to intercalary valves of the diatom Eucampia antarctica sensu lato . During the early Brunhes the winter sea-ice edge was positioned south from Site 745 . It started expanding northward, closer to the site location soon after 0 .4 Ma and progressed in a manner of a several wide oscillations . For approximately the last 0 .1 Ma the winter sea-ice edge oscillated less and retained similar range of oscillations . The ice edge oscillated in periods which correspond closely to that of Milankovitch oscillations of Earth obliquity, although the significance of individual periods appears to vary in time . 103

Postglacial marine diatom record of the Palmer Deep, Antarctic Peninsula (ODP Leg 178, Site 1098) 2. Diatom assemblages

“…antarctica and var. recta ), which have different distribution patterns [ Fryxell and Prasad , 1990; Kaczmarska et al , 1993]. Eucampia antarctica var.…”

Antarctic Sea Ice Proxies from Marine and Ice Core Archives Suitable for Reconstructing Sea Ice over the Past 2000 Years

“…These chains are composed of two pointy-horned terminal valves and a variable number of flat-horned intercalary valves. Low ratio values of terminal-to-intercalary valves indicate long chains that developed under no winter sea ice to loose winter sea ice conditions [153]. However, this proxy has not been intensively used because of generally low abundances of E. antarctica in sediment cores [154].…”

Antarctic records of precession‐paced insolation‐driven warming during early Pleistocene Marine Isotope Stage 31

“…The ratio of terminal to intercalary valves of Eucampia antarctica winter forms provides an estimate of water temperature and sea ice extent on the Antarctic continental shelf, with short chains reflecting very cold water [ Whitehead et al , 2005; Kaczmarska et al , 1993], as evident in Holocene sediments of McMurdo Sound, where terminal valves constitute >40% of the Eucampia population, based on ratio counts from 5 surface sediment samples from southern McMurdo Sound (Table 1). These counts augment the work of Leventer [1988], which did not include such assessment.…”

“…In LU 3.1, Eucampia antarctica var. recta consists of >99% intercalary valves (Table 1), indicating very long chains, thus reflecting production in open water and an absence of sea ice well into the transitional seasons; conditions suggesting annual average temperatures above 3°C [ Kaczmarska et al , 1993].…”