Brief description
Variations in microfossil records in sediments over time are used as proxies for changes in the ocean. One important record determined from microfossils is sea-ice cover which influences, and is influenced by, wind and ocean circulation, atmospheric conditions, and heat balance. Increasing emphasis is being placed on the predictive capabilities diatoms may bear in estimating Antarctic sea-ice, one of the important modulators of Southern Hemisphere climate. The purpose of this study was to estimate past sea-ice concentration and annual coverage at the site of core MD88-787 in the Southeast Indian Ocean. The accumulation of diatom microplankton assemblages in sediments being the proxy for these records of climatic change.A new method for sea-ice concentration and cover estimation from CABFAC derived factor analysis was developed during this project. Previous estimations of sea-ice have relied on other avenues of deriving limits to the maximum sea-ice edge, while the model developed here made use of modern sea-ice satellite observations combined with diatom distributions that are considered more closely linked to the sea-ice cover.
Three models were proposed which estimated sea-ice concentration in February and September, and annual sea-ice cover.
Lineage
Maintenance and Update Frequency: notPlanned
Statement: The original transfer function was established for foraminifera in the equatorial regions by Imbrie and Kipp (1971). Use of this transfer function model was found to be inappropriate for modelling sea-ice cover due to non-consistant variance and the large number of zero values in the sea-ice concentration data. A new two-stage model was developed, taking these features of the data into consideration, and selects appropriate factors from the CABFAC analysis in deriving both sea-ice concentration and sea-ice cover in months per year.
A sea-ice concentration of less than 15% is considered to represent open-ocean conditions due to the nature of the satellite interpretation of the reflected signal against weather effects and the interpretation of the sea-ice edge.
Parameters for Antarctic Diatom Database: Diatom species, Leanne K. Armand code, core code, core coordinates (degrees, decimal minutes), total number of specimens recorded in each core, % of old species, % of data used in 24 major species
Parameters for historical sea-surface temperature estimates: Core depth (cm), analyseries extrapolated age scale (ka) at 10cm interval, DTF commonality, SST Feb (oC), estimate of sea-ice February concentration (%), standard error sea-ice February concentration (%), estimate of sea-ice September concentration (%), standard error sea-ice September concentration (%), estimate of sea-ice months / year cover (mths per year), standard error sea ice month/year cover.
Parameters for the raw diatom counts: Core depth (cm), diatom species, diatom subtotal and silica subtotal
A sea-ice concentration of less than 15% is considered to represent open-ocean conditions due to the nature of the satellite interpretation of the reflected signal against weather effects and the interpretation of the sea-ice edge.
Parameters for Antarctic Diatom Database: Diatom species, Leanne K. Armand code, core code, core coordinates (degrees, decimal minutes), total number of specimens recorded in each core, % of old species, % of data used in 24 major species
Parameters for historical sea-surface temperature estimates: Core depth (cm), analyseries extrapolated age scale (ka) at 10cm interval, DTF commonality, SST Feb (oC), estimate of sea-ice February concentration (%), standard error sea-ice February concentration (%), estimate of sea-ice September concentration (%), standard error sea-ice September concentration (%), estimate of sea-ice months / year cover (mths per year), standard error sea ice month/year cover.
Parameters for the raw diatom counts: Core depth (cm), diatom species, diatom subtotal and silica subtotal
Notes
CreditCentre des Faibles Radioactivities mixte CNRS CEA (France)
Credit
Institute of Antarctic and Southern Ocean Studies (IASOS)
Institute of Antarctic and Southern Ocean Studies (IASOS)
Credit
Institut Français pour la Recherche et Technologie Polaires (IFRTP)
Institut Français pour la Recherche et Technologie Polaires (IFRTP)
Credit
Terres Australes et Antarctiques Françaises (TAAF)
Terres Australes et Antarctiques Françaises (TAAF)
Credit
Australian Postgraduate Research Award (APRA)
Australian Postgraduate Research Award (APRA)
Purpose
To estimate past sea-ice concentration and coverage in the Southeast Indian Ocean
To estimate past sea-ice concentration and coverage in the Southeast Indian Ocean
Issued: 18 09 2007
Data time period: 1988 to 1988
text: westlimit=145; southlimit=-56.50; eastlimit=145.5; northlimit=-56.00
text: uplimit=3030.4; downlimit=3020
Subjects
BIOLOGICAL CLASSIFICATION |
CRYOSPHERE |
Diatoms |
EARTH SCIENCE |
Ice Extent |
MICROALGAE |
OCEANS |
PLANTS |
SEA ICE |
Sea Ice Concentration |
biota |
core_depth |
environment |
estimate_sea-ice_concentration |
estimate_sea-ice_cover |
extrapolated_age_scale |
latitude |
longitude |
sea-ice_concentration_standard_error |
sea-ice_cover_standard_error |
taxonomic_group_count |
taxonomic_name |
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Other Information
Antarctic Diatom Database (App 3-2.pdf)
Historical sea-ice concentration and cover estimation at the location of core MD88-787 in the Southeast Indian Ocean (App_6-8__787.pdf)
Raw diatom counts through core MD88-787 (App 6-6 787.pdf)
Identifiers
- global : a48db300-671b-11dc-88d6-00188b4c0af8
