Browsing by Author "Howard, W"

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    First records of winter sea ice concentration in the southwest Pacific sector of the Southern Ocean
    (American Geophysical Union, 2015-10-15) Ferry, AJ; Crosta, X; Quilty, PG; Fink, D; Howard, W; Armand, LK
    We use a Generalized Additive Model (GAM) to provide the first winter sea ice concentration record from two cores located within the southwest Pacific sector of the Southern Ocean. To compliment the application of GAM, a time series analysis on satellite records of sea ice concentration data was used to extend the standard 13.25 year time series used for paleoceanography. After comparing GAM sea ice estimates with previously published paleo sea ice data we then focus on a new paleo winter sea ice record for marine sediment core E27-23 (59°37.1'S, 155°14.3'E), allowing us to provide a more comprehensive view of winter sea ice dynamics for the southwest Pacific Ocean. The paleo winter sea ice concentration estimates provide the first suggestion that winter sea ice within the southwestern Pacific might have expanded during the Antarctic Cold Reversal. Throughout the Holocene, core E27-23 documents millennial scale variability in paleo winter sea ice coverage within the southwest Pacific. Holocene winter sea ice expansion may have resulted from the Laurentide Ice Sheet deglaciation, increased intensity of the westerly winds, as well as a northern migration of the Subtropical and/or Sub-Antarctic Fronts. Brief consideration is given to the development of a paleo summer sea ice proxy. We conclude that there is no evidence that summer sea ice ever existed at core sites SO136-111 and E27-23 over the last 220 and 52,000 years, respectively. ©2015. American Geophysical Union.
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    New sea ice estimates over the last 49ky in the southeast Indian Ocean sector of the Southern Ocean
    (Australian Geosciences Council, 2012-08-05) Armand, LK; Quilty, PG; Howard, W; Burckle, L; Shemesh, A; Crosta, X; Cortese, G; Fink, D; Ferry, A
    Although many Quaternary records have allowed the study of major glacial-interglacial change in the Southern Ocean, Holocene records from deep-sea cores are few and far between and are currently limited to the South Atlantic. Low sedimentation rates combined with deep seafloors, and the high-nutrient, low-chlorophyll nature of the Southern Ocean are all in part responsible for the lack of decadal-to-centennial resolution records in the open-ocean environment. Our study is focused on an array of sedimentological, micropalaeontological and geochemical analyses conducted on the first open-ocean, high-resolution core study of Quaternary-Holocene sea-ice variability in the Southeast Indian Ocean; Eltanin piston core 27–23. In this presentation the results of sea ice estimates derived from diatom remains and tied to other physical and geological proxies will reveal the change from a sea-ice covered glacial maximum and deglacial transition through to the modern day. We report evidence of several Holocene ice edge advance episodes out to 59◦S, inclusive of the Antarctic Climatic Reversal. The addition of this record to existing, lower-resolution, sea-ice histories from regional cores MD88-787 and SO136-111 and in context to modern oceanographic fronts enables scenarios of regional palaeoceanographic change to be refined.