… and their distribution by regional water masses today and in the geological past
Marine researchers investigate how individual water masses move in the oceans in order to understand key processes in the ocean and to detect circulation changes. A water mass differs from the surrounding water by its properties (for example, temperature, salinity, oxygen concentration).
The Southern Ocean surrounding Antarctica is an extremely large ocean basin, in which water masses of different origins meet. Strong winds and large temperature differences in the individual water masses lead to a very dynamic ocean circulation. In several regions close to Antarctica, surface water cools down so much that it sinks and forms new, oxygen-rich Antarctic Bottom Water. This process is a crucial driver for the global ocean circulation and also affects storage of carbon dioxide in the ocean. Trace metals, which serve as nutrients for microorganisms, are also carried into the deep ocean in this way. But there are also other regional water masses that are important for the supply of oxygen and nutrients to the Southern Ocean.
Within the Marine Geosystems research unit at the GEOMAR Helmholtz Centre for Ocean Research Kiel, we are investigating whether and how well the origin of individual water masses in the Southern Ocean can be distinguished on the basis of their trace metal content. We are also interested in identifying the quantities of trace metals and nutrients that are released into the Southern Ocean from underneath the Antarctic Ice Shield. Also, by comparing present-day Southern Ocean trace metal signatures with data from marine sediments, we can estimate how distinct past Southern Ocean circulation was from today. From these comparative studies, we can also identify past periods of major Antarctic glacier melt and assess the consequences of this temporary enhanced retreat of Antarctic ice sheet for the Southern Ocean circulation.
- How well can the origin of individual water masses in today’s Southern Ocean be distinguished on the basis of their trace metal isotope signatures?
- To what extent can we also retrieve this information from marine sediments or other marine archives for the understanding of past ocean circulation patterns?
- How extreme is the human impact on the trace metal content of Antarctic waters? Are Antarctic water masses for example already substantially polluted with the heavy metal lead?
- Measurement and interpretation of trace metal isotope ratios in seawater and marine archives such as sediments or iron-manganese crusts.
- Determination of the main entry sources of selected trace metals and their incorporation into marine archives.
- Our work takes place in the Southern Ocean and in the clean room laboratory, where we process and measure samples under very clean conditions.
Dr. Marcus Gutjahr, GEOMAR Helmholtz Centre for Ocean Research Kiel