Deep ocean temperatures during Eocene greenhouse climates
Main content
Project description
Motivation (background):
On the current trajectory, and without mitigation, by the end of this century atmospheric carbon dioxide concentrations may reach levels last seen on Earth during the Eocene (56 to 34 million years ago) – an interval of extreme global warmth within which alligators lived in the Arctic and Antarctica supported a diverse tropical to temperature flora. Reconstructing these greenhouse climates provides a unique opportunity to better understand how the Earth system operates under atmospheric carbon dioxide levels similar to those we may see in the future. In addition to the overall warmth, Eocene climate appears to have been highly unstable and was punctuated by rapid warming events, known as ‘hyperthermals’, each lasting for a few 10´s to 100´s of thousands of years. These rapid warming events are closely coupled with transient carbon cycle perturbations, which were superimposed upon larger scale reorganisations of the carbon cycle, as evidenced by the global record of carbon isotopes in carbonates. However, the relationship between Eocene carbon cycle changes and climate, and the role of the deep ocean, remains enigmatic. This is in part because much of our understanding of Eocene temperatures relies on stable oxygen isotope records from deep-sea benthic foraminifera. Interpreting this record, however, is complicated by the fact that in addition to temperature, the classical oxygen isotope paleo-thermometer can also be influenced by other factors,
including changes in salinity which may have been greater under an intensified hydrological cycle in greenhouse climate states.
We have been working on reconstructing deep ocean temperatures using clumped isotope thermometry; a relatively new approach to derive robust temperature information from carbonates based on the ordering ("clumping") of stable isotopes within the molecules (Meckler et al., 2022). Using this approach, this masters project aims to reconstruct robust deep ocean temperatures for a select time interval in the Eocene to disentangle temperature and salinity changes in the existing benthic foraminiferal stable oxygen isotope records. The master student will join the DOTpaleo project team who are studying Paleogene climate through a combination of clumped isotope-based temperature reconstructions and climate modelling.
Research questions: How warm was the deep ocean during the Eocene? How variable was deep ocean temperature through time? Was deep ocean temperature different in different ocean basins?
Test (work):
Sediment samples will be wet-sieved and benthic foraminifera picked from the dried coarse fraction. Benthic foraminifera will be cleaned and analysed using a clumped isotope mass spectrometer, under guidance. The new data will be used in conjunction with other available data from our group and compared to published records from various proxies. The results will also be compared to existing climate model simulations generated within the DOTpaleo project.
Reference:
Meckler, A.N., Sexton, P., Piasecki, A.M., Leutert, T.J., Marquardt, J., Ziegler, M., Agterhuis, T., Lourens, L.J., Rae, J.W.B., Barnet, J., Tripati, A., Bernasconi, S.M., 2022, Cenozoic evolution of deep ocean temperature from clumped isotope thermometry, Science 377, 86-90
Proposed course plan during the master's degree (60 ECTS):
Suggested courses (can be discussed):
H24:
GEOV222 (10P)
GEOV324 (5P)
V25:
GEOV302 (10P)
GEOV231 (10P)
GEOV329 (10P) or GEOV342 (10P)
GEOV331 (5P)
H25:
GEOV300 (5P)
Felt- lab- og analysearbeid
approximately 6 months of laboratory work
The project is funded by: NFR DOTpaleo
