Arctic Ocean trace metal fluxes in an era of change (“ArcTrace”)

• Applicant: Dr. Stephan Krisch
• Subject Area: Oceanography
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567623735

Within the last two decades, the Arctic Ocean has seen a substantial increase in primary production (⁓60%) which is most likely supporting enhanced carbon export. However, little is known about the factors that control phytoplankton growth in the Arctic including macronutrient and micronutrient availability. The Arctic Ocean is subject to considerable change due to anthropogenic climate forcing. This change manifests in enhanced riverine discharge, increasing shelf erosion and sea ice decline including Atlantification of large parts of the Eastern Arctic Ocean all of which have ramifications on trace metal cycling and micronutrient availability, also in regions downstream to the Arctic Ocean. This project assesses trace metal and micronutrient fluxes, sources and sinks in the Arctic Ocean in 2024 and addresses their temporal change in relation to previous GEOTRACES expeditions to the region from 2007 and 2015. Samples and oceanographic data were collected onboard the research icebreaker “Polarstern” in later summer 2024 (PS144 or ‘ArcWatch 2’) in collaboration with the Alfred Wegener Institute. Combining physical (i.e. temperature, salinity, turbidity, fluorescence) and chemical data (i.e. dissolved and particulate trace metals and micronutrients, macronutrients, dissolved (in-)organic carbon), we will address the substantial knowledge gaps that exist in the transport of riverine and terrestrial-derived dissolved trace metals across the Central Arctic Ocean including the processes that control elevated trace metal transport. We will address supply and removal processes associated with the advection and shoaling of Atlantic Water (‘Atlantification’) and its effects on micronutrient availability and phytoplankton growth in the Eastern Arctic Ocean. From nutrient addition experiment (“bioassay experiments”) conducted during ArcWatch 2, we will determine the nature of phytoplankton nutrient limitation across the region. This will be the first time to constrain the factors controlling phytoplankton growth in the region by “in-situ” observations and will help to project feedbacks of climate change on the extent of primary production in the Eastern and Central Arctic Ocean. Our work includes the analysis of trace metal samples from the Nordic Seas from 2012 to investigate on the southern extent of Arctic Ocean trace metal export into the high-latitude North Atlantic Ocean, a region which net primary production likely depends on micronutrient supply from the upstream Siberian Arctic. Combined, this work extends the timeline of Arctic Ocean trace metal and micronutrient cycling at a sub-decadal resolution and is crucial for the projection of future ecosystem services including primary production, carbon sequestration and food web structure in the Central Arctic and high-latitude North Atlantic Ocean.

• DFG Programme: Research Grants