The application of single specimen foraminiferal isotope analyses to investigate seasonality in the Southern Ocean

• Main Author: Mikis, Anna
• Format: Thesis
• Language: English
• Published: 2017
• Subjects: Antarctic; Antarctic Peninsula; Scotia Sea; Southern Ocean; The Antarctic; Antarc*; Neogloboquadrina pachyderma; Sea ice
• Online Access: https://orca.cardiff.ac.uk/id/eprint/109233/; https://orca.cardiff.ac.uk/id/eprint/109233/1/2018mikisadphd.pdf; https://orca.cardiff.ac.uk/id/eprint/109233/2/mikisad.pdf

The Antarctic Peninsula and the surrounding Southern Ocean are some of the most climatically sensitive regions on Earth. The West Antarctic Peninsula (WAP) experienced a ~3.4°C warming during the 20th century which was accompanied by widespread glacial melting. In contrast, 21st century air temperature records in the northern Antarctic Peninsula show a decreasing trend indicating large scale natural decadal-scale climate variability at that location. Atmospheric and oceanographic variability in the WAP have also been observed in Holocene climate records showing variable meltwater discharge relating to the frequency of La Niña events and summer insolation during the late Holocene. Single specimen foraminiferal isotope analysis has been successfully used to study changes in seasonal variability in the tropical regions relating to El Niño-Southern Oscillation (ENSO). In this thesis, I investigate the applicability of this method to study seasonal changes in environmental conditions in the high latitudes over a range of timescales. In the Scotia Sea, a modern record of the polar foraminifera species, Neogloboquadrina pachyderma, shows temperature related distribution and δ18O signature, the presence of multiple morphotypes, as well as variable calcification depths and vital offsets related to biological processes as determined by the single specimen isotope analysis. A six-year long sediment trap-derived Neogloboquadrina pachyderma record of abundance, morphology, and single specimen δ18O showed that all these parameters are driven by seasonal changes in sea ice concentration and food availability - relating to chlorophyll α concentration and sea surface temperature - at the Antarctic Peninsula. The Neogloboquadrina pachyderma record highlights inter-annual variability, relating to the teleconnections between ENSO/Southern Annular Mode and the high latitude atmospheric setting, proving its suitability to investigate seasonality changes. Finally, in the Scotia Sea, a single specimen Globorotalia inflata δ18O record ...