Atlantic Ocean nutrient, carbon and oxygen supply in the Pliocene greenhouse world

Project description
Background:One large unknown in future climate predictions is how changes in ocean structure, circulation and primary production may reorganize the global nutrient, oxygen and carbon distribution. A future concern is that Atlantic meridional overturning circulation (AMOC) will slow and less nutrients and oxygen will be transported from the Southern Ocean to the global ocean, which will have large consequences for marine life.The Pliocene (5.3–2.6 Ma) is the most recent geologic time interval with sustained global warmth (1.8–3.6°C warmer than preindustrial) and levels of greenhouse gases comparable to today (330–495 ppmv) and can thus serve as an analogue for future climate change. The master student will employ biogeochemical proxy analysis (e.g., benthic foraminiferal stable isotope analysis) on Pliocene marine sediment deposits to reconstruct past South Atlantic Ocean structure, nutrient and oxygen ventilation/availability, and primary productivity. By reconstructing past South Atlantic Ocean structure the student could give valuable insight into instabilities in ocean biogeochemical cycling and productivity in a greenhouse world.Scientific Problem/Question(s):- What is the mode, strength, and variability of ocean ventilation in equilibrium with our current greenhouse atmosphere? How will this ocean state impact global nutrient supply and global productivity? The student will address this by examining the Pliocene South Atlantic Ocean circulation and preformed nutrient, carbon and oxygen export by the Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water (SAMW) to the global thermocline.

Proposed course plan during the master's degree (60 ECTS):
Spring 2024: GEOV231 (10 credits), GEOV331 (5 credit), GEOV 342 (10 credits)
Fall 2024: GEOV222 (10 credits), GEOV300 (5 credits), GEOV324 (5 credit)
Spring 2025: GEOV302 (10 credits)

Field- lab- and analysis work
Spring 2024 - Autumn 2024: Work with South Atlantic marine sediment cores - sample preparation and microscope work selecting foraminifera for analyses.
Spring 2025: Stable isotope analyses in FARLAB. E.g. Multi-species benthic foraminifera stable carbon isotope (δ13C) records. Nitrogen isotopic ratio of bulk organic matter (δ15Norg). CaCO3 accumulation rates for primary productivity.
Spring 2025-Autumn 2025: Data analysis, writing thesis.Estimated total duration of lab work: 6 months