Physical and biogeochemical responses to Antarctic sea ice loss: what are the implications for ocean carbon uptake?

Dr Alice Marzocchi, Dr Peter Brown, Dr Alessandro Silvano, Prof Alberto Naveira-Garabato, Caroline Holmes, British Antarctic Survey (BAS),

Project Overview 

This project will use observations from satellites, autonomous sensors and floats, combined with climate model outputs, to investigate how physical and biological processes (and the resulting carbon dioxide uptake) respond to changing sea ice conditions in the Southern Ocean (SO), the most important region globally for ocean anthropogenic-carbon uptake.

Project Description 

The SO is responsible for the uptake of more than 40% of anthropogenic CO2 and 75% of anthropogenic heat by the ocean. However, mechanisms and drivers of SO carbon cycling are poorly understood, partly due to the complex and variable influence of sea ice: it acts as a physical barrier to gas exchange, but also modulates light availability for phytoplankton growth, which influences the biological pump and carbon sequestration. The balance between these two effects is likely to shift as Antarctic sea ice declines, making this an urgent research question in light of current rapid changes. However, the direction and magnitude of change in carbon uptake are highly uncertain, as there is low confidence in the ability of state-of-the-art climate models to capture anthropogenically forced changes in sea ice and the timing, sign and magnitude of the SO CO2 seasonal cycle.

This project will leverage recently funded Antarctic projects, combining new observational approaches (autonomous robots, remote sensing) and modelling tools, to better understand ocean-ice processes in the SO, the role of biology, and how these will change into the future.

The student will interrogate in-situ datasets, data assimilation/inverse/climate models (e.g. B-SOSE, ECCO-Darwin, CMIP) and apply statistical tools, enabling the extraction of key relationships between ice-ocean-atmosphere processes and interactions on biologically-driven CO2 uptake.

The project will improve our understanding of SO physical-biogeochemical interactions, and more skilfully predict future changes, in a field of study of great societal interest, with the support of a multidisciplinary team with a diverse range of expertise.

University of Southampton/National Oceanography Centre

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at NOC, with visits to the British Antarctic Survey.

This PhD – ideal for someone with a physical, numerate, or biogeochemical background – will train the student in computer programming and handling/processing/interpreting of ‘big data’ archives, essential skills in international environmental research.

Specific training will include:

1)    University of Southampton courses – e.g. Physical Oceanography, Climate Dynamics, Biogeochemical Cycles.

2)    Theory/optimization/manipulation and data analysis of remote sensing products and autonomous technologies such as profiling floats.

3)    Inverse models, and handling/analysis of ocean/climate model output.

4)    Time series analyses, statistical tools.

5)    Attend national/international conferences and summer schools.

Seagoing experience, handling equipment, observations/data collection during Southern Ocean fieldwork.

Eligibility & Funding Details: 
Background Reading: 

(1)   SO-CHIC consortium, et al. "Southern Ocean carbon and heat impact on climate." Philosophical transactions of the royal society A 381.2249 (2023): 20220056.

(2)   Mongwe, N. Precious, Marcello Vichi, and Pedro MS Monteiro. "The seasonal cycle of pCO2 and CO2 fluxes in the Southern Ocean: diagnosing anomalies in CMIP5 Earth system models." Biogeosciences 15.9 (2018): 2851-2872.

Zhou, Shenjie, et al. "Slowdown of Antarctic Bottom Water export driven by climatic wind and sea-ice changes." Nature Climate Change (2023): 1-9.