Meeting Documents

Modelling the carbon cycle across the Arctic land-ocean continuum: a case study of the Southeastern Beaufort Sea

Abstract

Five of the world's largest rivers discharge into the Arctic Ocean (AO), conveying large amounts of terrestrial matter into its coastal waters. In the context of global warming and accelerating permafrost thaw, the response of the coastal AO to changing biogeochemical river runoff remains highly uncertain, which makes the assessment of air-sea CO₂flux challenging in this region. To better understand the impact of terrestrial dissolved carbon release (organic tDOC and inorganic tDIC) on AO air-sea CO₂ flux, we use a state-of-the-art ocean/sea-ice/biogeochemical model (ECCO-Darwin) specifically configured to simulate the dynamic Mackenzie Delta/Southeastern Beaufort Sea region (SBS; western AO). The model includes both daily riverine tDIC and tDOC runoff estimated in this region.The terrestrial DOC runoff is split into two pools with different microbial degradation rates, representing semi-labile and semi-refractory species. We first quantify the effects of dissolved carbon runoff on coastal CO2 flux over synoptic-to-interannual timescales. We find that tDIC river runoff is responsible for a CO₂ outgassing of 0.40 TgC yr^-1 over the 2000-2019 period, equivalent to twice the contribution of tDOC (0.23 TgC yr^-1). Our simulations also exhibit strong interannual variability in localized CO₂ fluxes driven by the intensity of river discharge. We then assess the sensitivity of the model to microbial remineralization rates and evaluate model skill against in-situ observations. Our numerical study is particularly relevant and timely as the intensified land-to-sea coupling strongly responds to climate change and drives carbon cycling along Arctic Ocean coastal waters and shelves.View Document (AGU) »