Silicon isotopes highlight the role of glaciated fjords in modifying coastal waters

Hatton, J.E.; Ng, H.C.; Meire, L.; Woodward, E.M.S.; Leng, M.J. ORCID: https://orcid.org/0000-0003-1115-5166; Coath, C.D.; Stuart-Lee, A.; Wang, T.; Annett, A.L.; Hendry, K.R. ORCID: https://orcid.org/0000-0002-0790-5895. 2023 Silicon isotopes highlight the role of glaciated fjords in modifying coastal waters. Journal of Geophysical Research: Biogeosciences, 128 (7), e2022JG007242. 17, pp. https://doi.org/10.1029/2022JG007242

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Text (Open Access) © 2023. The Authors. JGR Biogeosciences - 2023 - Hatton - Silicon Isotopes Highlight the Role of Glaciated Fjords in Modifying Coastal Waters.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (1MB) | Preview

Abstract/Summary

Glaciers and ice sheets are experiencing rapid warming under current climatic change and there is increasing evidence that glacial meltwaters provide key dissolved and dissolvable amorphous nutrients to downstream ecosystems. However, large debate exists around the fate of these nutrients within complex and heterogenous fjord environments, where biogeochemical cycling is still often poorly understood. We combine silicon (Si) concentration data with isotopic compositions to better understand silicon cycling and export in two contrasting fjordic environments in south-west Greenland. We show that both fjords have isotopically light dissolved silicon (DSi) within surface waters, despite an apparently rapid biological drawdown of DSi with increasing salinity. We hypothesise that such observations cannot be explained by simple water mass mixing processes, and postulate that an isotopically light source of Si, most likely glacially-derived amorphous silica (ASi), is responsible for further modifying these coastal waters within the fjords and beyond. Fjord to coastal exchange is likely a relatively slow process (several months), and thus is less impacted by short-term (< seasonal) changes of glacial meltwater input into the fjord, which has implications when considering the role of glacial meltwaters on nutrient export beyond the shelf break. We highlight the need for isotopic studies combined with dissolved and particulate nutrient concentration analysis to provide a more detailed analysis into the biogeochemical cycles within these highly dynamic fjord environments.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1029/2022JG007242
ISSN:	21698953
Additional Keywords:	Silicon Isotope Geochemistry, Fjord Nutrient Cycling, Silicon Cycling, Greenland Ice Sheet
Date made live:	13 Jun 2023 09:02 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/534707

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