Modelling the CO2 dynamics in the Laptev Sea, Arctic Ocean: Part I

Global temperature observations during the last century show that the largest increase over the last decades has been manifested in the Arctic, particularly within the Siberian region. The Arctic Ocean is a harsh region with few field studies, resulting in limited temporal and spatial resolution of hydrographical data. One way to circumvent this deficit is to utilise a model that represents processes which are known to possibly impact climate. This has been done for the carbon system in the Laptev Sea of the Arctic Ocean by utilising a one-dimensional, time dependent coupled physical–biochemical model. This model was validated by observational data of temperature, salinity, phosphate, oxygen and the carbon system.The model simulation reveals that wind pattern is essential for the exchange of dissolved inorganic carbon with the surrounding seas and the carbon dioxide exchange with the atmosphere. The latter is largely driven by the surface water partial pressure of carbon dioxide that is impacted by primary production, water temperature, vertical mixing and river runoff. The model shows that the timing of these factors is critical for the flux of carbon dioxide as is the sea ice coverage. Modelled primary production starts after the disappearance of sea ice and the spring flood has reached the area in June, it peaks in a short time and decreases slowly to negligible levels in mid September. This primary production causes an undersaturation of carbon dioxide with up to 200 μatm during the productive season after which the partial pressure of carbon dioxide increases as the carbon dioxide rich deep water mixes up into the surface layer. However, surface water partial pressure of carbon dioxide is undersaturated all through the year, except for some years when there is a short period of outgasing in the beginning of June. This outgasing occurs when the ice breaks up late and river runoff accumulates under the ice.

► A 1-D coupled model was applied to deduce the C-cycle of the Laptev Sea.
► It shows an undersaturation of CO2 up to 200 μatm caused by primary production.
► In the fall the surface waters pCO2 increase to about atmospheric level.
► This rise occurs when the decay products mixes up into the surface layer.