On the Role of Missed Components of Carbon Cycling in the East Siberian Arctic Shelf

The widest and shallowest East Siberian Arctic Shelf (ESAS) acts as an important region for producing and processing of organic matter before the material is transported into the Arctic Ocean. Up to 100% of the total organic carbon (TOC) in the ESAS sediments is terrestrial by origin (TOCterr). TOCterr flux in the ESAS integrates riverine and coastal erosion signals transforming within the land-shelf-atmosphere system. Ongoing warming causes thawing of the permafrost underlying majority of river watersheds and more than 80% of the ESAS area; this process could accelerate river discharge, carbon losses from soils, involvement of old carbon to the modern carbon cycle and mobilization previously originated CH₄ stored within seabed deposits. Decreasing uncertainties in current budgets and understanding further change of carbon fluxes over the Arctic Ocean is critical to assessing how regional carbon cycling may impact an already warming climate.

All existing carbon balance estimations for the Arctic Ocean are incomplete and unreliable because: 1) they reflect lack of knowledge on the critical region of the Arctic marine system, which is the East Siberian Arctic Shelf (ESAS) composing ~30% of the total Arctic shelf area; 2) annual budgets do not reflect spatial and temporal variability of carbon fluxes; 3) TOC efflux accounted for the budget does not apportion processes, which accompany its transformation within land-shelf system; 4) gaseous components of carbon cycling (CO₂ and CH₄) were not incorporated into the budget.

Here we present our multi-year data (1999–2009) which show that: 1) current estimates of riverine solid runoff, used for budget estimations, does not reflect the fact that majority of riverine TOC settles in delta channels and never reach the shelf; 2) current estimates of coastal erosion input does not reflect the fact that significant part of eroded TOC transforms to CO₂ and releases to the atmosphere; 3) annual outgassing from the shallow ESAS of ~8 Tg C-CH₄ is comparable with total methane emissions from all coastal seas of the World Ocean; 4) annual release of CO₂ from the shallow ESAS to the atmosphere can reach up to 10 Tg C-CO₂; 5) incorporating theses components into the current budgets could drastically change our understanding of processes ongoing over the entire arctic marine system.