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

Project description
One large unknown in future climate predictions is how changes in ocean structure, circulation and primary productivity may reorganize the global nutrient, oxygen and carbon distribution. A future concern is that Atlantic meridional overturning circulation (AMOC) will slow down, and less heat, carbon, nutrients and oxygen will be transported to the North Atlantic. The mid-Pliocene Warm Period (mPWP, ~3.2 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 marine sediment deposits from the mPWP to reconstruct past North Atlantic Ocean structure, nutrient and oxygen availability, and primary productivity. The study material comes from the Feni Drift marine sediment core; Ocean Drilling Program (ODP) Site 981 (55° 29’N, 14° 39’W), ideally situated at intermediate water depth (~2,200 m) to unpack the variance in water masses coming from North Atlantic Deep Water and Southern Ocean sourced water. By reconstructing past centennial-scale variability in North Atlantic Ocean structure, the student could give valuable insight into instabilities in ocean biogeochemical cycling and productivity in a greenhouse world.

- What is the mode, strength, and variability of Atlantic meridional overturning circulation (AMOC) 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 in high temporal resolution the Pliocene North Atlantic Ocean structure and nutrient, carbon and oxygen transport/availability in the global thermocline.

Proposed course plan during the master's degree (60 ECTS):
Spring 2025: GEOV231 (10 credits), GEOV302 (10 credit), GEOV 342 (10 credits)
Fall 2025: GEOV222 (10 credits), AG353/10 ECTS (10 credits)
Spring 2026: AG342/10 ECTS (10 credits)

Field- lab- and analysis work

Spring 2025:  Work with North Atlantic marine sediment core ODP Site 981 - sample preparation and microscope work selecting foraminifera for analyses.
Fall 2025: Stable isotope analyses in FARLAB.  E.g. Multi-species benthic foraminifera stable carbon isotope (δ¹³C) records. Possibly also CaCO₃ accumulation rates for primary productivity and/or Nitrogen isotopic ratio of bulk organic matter (δ¹⁵N_org).
Spring - Autumn 2026: Data analysis, writing thesis.

Estimated total duration of lab work: 6 months.