Award: OCE-1540254

During this project we collected over 600 seawater samples from a research cruise in the Arctic ocean, and then measured the concentrations and stable isotope ratios of many different metals in those water samples in order to better understand life in Arctic oceans.

The samples were collected from the US Coast Guard icebreaker Healy, as part of the GEOTRACES program which aims to study the distribution of trace-metals throughout the world ocean. Our group received water samples collected from the ?GEOTRACES rosette? which collects seawater into bottles from deep within the ocean, and which is built with special materials including titanium and teflon in order to avoid contamination of trace metals. We also received particle samples collected with special trace-metal clean underwater pumps, and samples of snow and ice taken by hand or with small hand-held pumps from near the ship.

On all of these samples, we measured the concentration of biologically important metals including iron, zinc, cadmium, copper, nickel, and manganese. We also made very difficult measurements of δ⁵⁶Fe, δ⁶⁶Zn, and δ¹¹⁴Cd, which are the stable isotope ratios of iron, zinc and cadmium.

This data helps us to better understand the biological role of metals as nutrients for photosynthetic algae which live in the Arctic Ocean. Just as humans need metals such as iron, zinc, and manganese to survive, marine phytoplankton need these metals, and they must get them from seawater in order to grow. By studying the distributions of these metals in the Arctic Ocean, we were able to better understand how they got into seawater. One nice example of this is the distribution of iron (Fe) and iron isotopes (δ⁵⁶Fe) in the Arctic (see attached figures). We observe high concentrations of Fe near the continental shelves which have a low δ⁵⁶Fe, showing us that Fe in this region comes from low-oxygen sediments on the shallow continental shelves. We also observe high Fe concentrations near the North Pole, however here the δ⁵⁶Fe values are much higher. This shows us that Fe near the North Pole comes from rivers in the Russian sector of the Arctic Ocean. As the Arctic ocean experiences the effects of climate change, we can compare our data to future measurements of Fe concentrations and isotope ratios to see how inputs of iron are changing.

Last Modified: 03/04/2020
Modified by: Seth G John