Work

Variation in chemical composition of dissolved organic matter during the winter to spring transition in the northern Barents Sea

Year: 2025

Type: article

Abstract: DOM molecular characterization data from the Arctic Ocean is scarce, especially during the winter, which is a crucial period for water mass mixing and carbon cycling. The northern Barents Sea extending into the Arctic Ocean is experiencing global warming at a rate 5-7 times faster than the global average, leading to drastic chemical, physical and ecosystem changes. We sampled a transect along this region during early winter (December), late winter (March) and spring (May) and analyzed seawater samples using high-resolution mass spectrometry. Our mass spectrometry-based results indicate that ionizable DOM compounds were less saturated during early winter relative to both late winter and spring, shown by weighted average hydrogen to carbon atomic ratios (H/Cwa) (-0.029, Mann-Whitney U test, p-value < 0.001). Early winter also correlated with higher dissolved organic carbon (DOC), higher weighted average aromaticity index (AImod) and increase in relative intensities of CHO formulas over heteroatom (N, S)-containing formulas, thus supporting the presence of DOM with higher recalcitrance and potentially higher allochthonous DOM input. The increase in DOM lability from early to late winter correlated with an increase in nitrogen containing formulas which could point to DOM products of viral processing during winter period. Atlantic Water influenced stations (indicated by higher temperature and salinity) correlated with compounds of higher weighted average molecular weight and oxygen to carbon atomic ratio (O/C) highlighting the role of abiotic processes in shaping DOM composition. Our findings suggest that the Arctic environment undergoes substantial changes in DOM reactivity and bioavailability throughout the winter, with potential implications for global carbon transport and storage in the future Arctic. As Atlantic water increasingly influences the Arctic and potentially raises dissolved organic carbon (DOC) levels, carbon decomposition rates may rise, particularly during late winter.

Source: Marine Chemistry

DOI: 10.1016/j.marchem.2025.104517

Authors: Maria G. Digernes, Jeffrey A. Hawkes, Oliver Müller, Stephen G. Kohler, Murat V. Ardelan

Institutions: Norwegian University of Science and Technology, Uppsala University, University of Bergen

Language: English

Topic: Marine and coastal ecosystems

Subfield: Oceanography

Field: Earth and Planetary Sciences

Domain: Physical Sciences

SDGs: Climate action, Life below water

Open Access status: hybrid

Estimated APC paid: $3,280