Reverse and Submarine Weathering in Glacially Influenced Arctic Fjords

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

When mineral particles reach the ocean floor, they often undergo biological or chemical transformations that turn them into new mineral phases and also result in the uptake from or release of elements to the surrounding seawater. One set of these reactions involve silicate minerals, which are composed of silica and oxygen and a range of other elements, such as iron and aluminum. These seafloor reactions are important because they affect the chemical composition of the ocean and its pH. In this project, we aim to study these reactions in Arctic fjords. Fjords are long, narrow ocean inlets that were formed by glaciers moving over the landscape in the past. Many fjords still have glaciers located at their inner end today which deliver meltwater and sediment to fjord waters. Climate change is resulting in the rapid melting of these glaciers. We are interested in understanding the specific silicate mineral reactions that are occurring, what elements they are taking up or releasing, and how climate change may affect these processes. We will collect seafloor sediment samples for this project from Kongsfjorden, Svalbard, and analyze them using a range of chemical methods. Additionally, we will carry out laboratory incubation studies where we will add silicate minerals formed by ocean algae to fjord sediments and observe what happens to them. Over long time scales, the inputs of major and minor elements to the ocean by rivers and hydrothermal vents has to be balanced by removal mechanisms of these elements in the marine realm in order for ocean chemistry to remain relatively constant. A long-debated process that sequesters elements in ocean seafloor sediments and affects seawater pH is reverse weathering which involves the transformation of biogenic silica, such as diatom frustules, to new silicate (clay) minerals. Many aspects of this process still remain unknown, such as reaction rates and products, and global distribution. Previous studies of this process have focused mainly on tropical coastal ocean systems. Coastal polar regions, including glacially influenced fjords, likely represent another hotspot of reverse weathering because they receive high inputs of key “ingredients”: biogenic silica and reactive iron and aluminum oxide minerals. At the same time, climate change drives the retreat of Arctic glaciers and is expected to strongly modify sediment delivery to and carbon cycling in these fjords. This project will fill key gaps in our knowledge of the pathways and products of the reactions involving silicate minerals in sediments and the impacts of these processes on the removal of dissolved ions from seawater in glacially influenced fjords. We will collect sediment samples for this project from Kongsfjorden, Svalbard, and analyze them using a range of geochemical techniques. Additionally, we will carry out incubation studies using diatom frustules and fjord sediments. The outcomes of this study will help accurately constrain the possible impacts that climate change in rapidly changing Arctic coastal environments has on larger scale oceanic processes and construct predictive models of elemental cycling and biogeochemical responses in the future ocean. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.