Core-top versus Holocene samples from the Fram Strait and the Nordic Seas: Restrictions in Mg/Ca-paleotemperature estimations in high-latitude bottom waters

• Main Authors: Werner, Kirstin, Marchitto, Thomas M., Not, Christelle, Hass, H. Christian, Spielhagen, Robert F., Husum, Katrine
• Format: Conference Object
• Language: unknown
• Published: 2014
• Subjects: Arctic; Arctic Ocean; Norwegian Sea; Boyer; Fram Strait; Nordic Seas
• Online Access: https://oceanrep.geomar.de/id/eprint/27634/

Mg to Ca ratios of the epibenthic foraminifer species Cibicidoides wuellerstorfi have been identified to be strongly controlled by temperature and thus to have great potential for reconstructing bottom water temperatures, especially from the lower end of the temperature range (0-6°C; Tisserand et al., 2013). In the Fram Strait, where main water mass exchanges between the Arctic Ocean and the world’s oceans occur, new temperature estimation tools independent from faunal assemblages can help to better understand the complex interaction of different water masses with possible implications to changes in the meridional overturning circulation and the heat flux to the Arctic Ocean. Furthermore, Mg/Ca temperatures can help unravelling the local impact (e.g., of brine-enriched waters) from general trends in bottom water circulation. In order to apply Mg/Ca-derived temperatures to paleo-records from the Fram Strait, a calibration relationship between modern Mg/Ca ratios to bottom water temperatures which fits the environmental conditions of the Fram Strait needs to be developed. We therefore studied Mg/Ca ratios of C. wuellerstorfi in a set of coretop samples from the Fram Strait and the Norwegian margin where bottom temperatures range between -0.5 and -1°C. For the calibration to modern temperatures, we used modern oceanographic data from both existing conductivity-temperature-depth (CTD) casts and the World Ocean Data Base 2013 (Boyer et. al., 2013). Benthic Mg/Ca ratios are relatively high suggesting a preference of C. wuellerstorfi to incorporate Mg at temperatures below 0°C. Although no correlation has been found to existing temperature calibrations using higher temperature ranges (0-6°C), the data are in line with existing Mg/Ca data from C. wuellerstorfi from the Norwegian Sea and the Fram Strait (Martin et al., 2002; Elderfield et al., 2006).While correlation between Mg/Ca ratios to either temperature or salinity is difficult to constrain, better correlation exists to water depth. We therefore consider the ...