Biogeochemical cycling of trace metals in a changing Arctic Ocean

Project Rationale:

The Arctic Ocean is the most rapidly warming ocean on our planet, but the consequences of ice melt on primary productivity, which underpins the entire Arctic ecosystem, are not clear. Although primary productivity has already increased [1], future trends have proven hard to predict because of ongoing debate on the supply of trace metals that are essential for phytoplankton growth. For example, retreat of sea ice may reduce supplies of iron to growth-limiting levels in the central Arctic Ocean [2], whereas increased mixing between onshore and offshore waters may enhance metal input from shelf seas.

The aim of this study is to determine the processes that control the availability of trace metals in the Arctic Ocean. This will be done via collection of seawater samples and observational data across environmental gradients (temperature, nutrients, metals) in the eastern Arctic Ocean, employing state-of-the-art metal isotope analyses. This work will provide a robust framework for understanding the importance of trace metal supply on primary productivity and the carbon cycle in the Arctic Ocean under future ice-free conditions.

Methodology:

The student will collect samples for this project during a 35-day research cruise to the Barents Sea and Fram Strait in the eastern Arctic Ocean, as part of the NERC-funded N-ARC (Nitrogen fixation in the Arctic Ocean) project. Recent work (e.g. [3]) has shown that analyses of the stable isotopic composition of trace metals provides unique information for identifying metal sources, as well as the processes that modify metal concentrations. This study will combine analyses of iron (Fe) and chromium (Cr) isotopes, with analyses of metal speciation, to identify the controls on metal distributions in the eastern Arctic Ocean. Armed with this information, the student will work with other members of the N-ARC project to provide a pan-Arctic view on changes in primary productivity and the carbon cycle in an ice-free Arctic Ocean.

Training:

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 the School of Ocean and Earth Science. Specific training will include:

• Working at sea and developing practical skills (including trace metal sampling techniques) needed for the project.
• Training in state-of-the-art analytical techniques including multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for accurate and precise analysis of iron and chromium isotopes. Analytical work will be undertaken in our world-class Geochemistry facilities.
• Training in the analysis of metal speciation, including the development of new techniques for isotopic analysis of Cr(III) and Cr(VI).

The student will also work closely with other members of the N-ARC team throughout the project.