Variability of past ocean circulation

Project description
Understanding the Ocean's crucial role in shaping climate and the vulnerability of ocean currents to climate change is important for tackling today's environmental challenges. Of particular interest is the deep overturning circulation that connects the surface and the deep ocean because it may represent a tipping point of the climate system. The subpolar North Atlantic emerges as a key area for overturning circulation due to the water mass transformation and deep water formation processes occurring there. Exploring variability in this region, particularly over long time-scales, can provide valuable insights into the variability and stability of the overturning circulation (Årthun et al., 2021).

The aim of this project is to:

• Enhance our understanding of circulation variability in the subpolar region and its response to past environmental conditions
• Assess the accuracy and reliability of climate models simulating warmer than present conditions

Approach:
Using output from global climate models simulating the last interglacial (Otto-Bliesner et al., 2021) you will investigate circulation variability during the last interglacial—a period that, like our projected future, was warmer than present in the (sub)polar North Atlantic. By running the FAME model (Roche et al., 2018) you will simulate how planktonic foraminifera respond to past climate and ocean circulation variability. The simulation results will provide a new, physically consistent, approach for using foraminiferal proxy records to diagnose how, and how much, circulation changed in the past. Through comparison to existing proxy reconstructions, you will also validate the accuracy and reliability of model simulations of a warmer world.

The guiding hypotheses for this project are:
Circulation variability produces distinct fingerprints that can be identified in foraminiferal proxies. Current state-of-the-art climate models fail to capture the circulation and climate instability occurring in a recent geologic analogue for warmer than present conditions.

This project will give you insight into both climate modelling and paleo-ocean records. Through your research, you will learn about ocean processes, especially in the North Atlantic, and their impact on the climate system.

References:
Roche, Didier M., et al. "FAME (v1. 0): a simple module to simulate the effect of planktonic foraminifer species-specific habitat on their oxygen isotopic content." Geoscientific Model Development 11.9 (2018): 3587-3603.
Årthun, Marius, et al. "Mechanisms of decadal North Atlantic climate variability and implications for the recent cold anomaly." Journal of Climate 34.9 (2021): 3421-3439.
Otto-Bliesner, Bette L., et al. "Large-scale features of Last Interglacial climate: results from evaluating the lig127k simulations for the Coupled Model Intercomparison Project (CMIP6)-Paleoclimate Modeling Intercomparison Project (PMIP4)." Climate of the Past 17.1 (2021): 63-94.

Proposed course plan during the master's degree (60 ECTS):
GEOV222 / Paleoklimatologi (10ETCS)
GEOV331 / Utvalgte emner i paleoseanografi (5ETCS)
GEOV302 / Dataanalyse i geovitenskap (10ETCS)
GEOV231 / Maringeologisk felt- og laboratoriekurs (10ECTS)
SDG213 / Klimaendringar - årsaker og konsekvensar (10ECTS)

Prerequisites
Potential candidates for this project should have an interest in computer modelling (particularly in Python), though prior experience is not required. Please feel free to reach out for any further inquiries.

Field, lab and/or analysis work
This project focuses on investigating the output of global climate models and the representation of variability in foraminiferal records. An existing model will be used to simulate the d18O of foraminferal calcite. This will be done in close collaboration and with help of the supervisors. Note that laboratory work is not planned as part of this project.