Mg/Ca ratios of single planktonic foraminifer shells and the potential to reconstruct the thermal seasonality of the water column.

Haarmann, Tim, Hathorne, Ed C. , Mohtadi, Mahyar, Groeneveld, Jeroen, Kölling, Martin and Bickert, Torsten (2011) Mg/Ca ratios of single planktonic foraminifer shells and the potential to reconstruct the thermal seasonality of the water column. Open Access Paleoceanography, 26 (3). PA3218. DOI 10.1029/2010PA002091.

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Mg/Ca ratios of surface and subsurface dwelling foraminifera provide valuable information about the past temperature of the water column. Planktonic foraminifera calcify over a period of weeks to months. Therefore, the range of Mg/Ca temperatures obtained from single specimens potentially records seasonal temperature changes. We present solution-derived Mg/Ca ratios for single specimens of the planktonic foraminifera species Globigerinoides ruber (pink), Globigerinoides ruber (white), and Globorotalia inflata from a sediment trap off northwest Africa (20°45.6′N, 18°41.9′W). Cleaning of single specimens was achieved using a flow-through system in order to prevent sample loss. Mg/Ca ratios of surface dwelling G. ruber (pink) show strong seasonality linked to sea surface temperature. Mg/Ca ratios of G. ruber (white) do not show such seasonality. Subsurface dwelling G. inflata flux is largest during the main upwelling season, but Mg/Ca ratios reflect annual temperatures at intermediate water depths. The sediment trap time series suggests that changes in the range of Mg/Ca ratios exhibited by single specimens of G. ruber (pink) and G. inflata from the sedimentary record should provide information on the past temperature range under which these species calcified. Statistical analysis suggests detectable changes in the Mg/Ca range are ≥0.80 mmol/mol (G. ruber (pink)) and ≥0.34 mmol/mol (G. inflata). For G. ruber (pink), such changes would indicate changes in the seasonal sea surface temperature range >4°C or a shift in the main calcification and reproductive period. For G. inflata, such changes would indicate >1.7°C changes in the thermocline temperature or a change in the depth habitat.

Document Type: Article
Keywords: Paleoceanography; Globigerinoides ruber; planktonic foraminifera; seawater temperature seasonality; single specimen Mg/Ca
Research affiliation: MARUM
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2010PA002091
ISSN: 0883-8305
Date Deposited: 08 Dec 2011 13:12
Last Modified: 23 Sep 2019 16:47

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