EXPEDITIONS

 

The main purpose of this comprehensive and multidisciplinary research project is to achieve a better understanding of basic mechanisms and factors that are responsible for integrating the continental-scale terrestrial and in situ marine biogeochemical signals, determined as a response of the arctic ecosystem to ongoing climate change, into the marine environment and their further transfer by means of Siberian arctic shelf waters. Carbon input, propagation, fate in the shelf waters, and resulting output to the atmosphere as carbon dioxide (CO2) and CH4 will be quantified to update the regional carbon budget. The overall goal of the project is to provide a quantitative, observationally based assessment of the dynamics of different components of the ESAS carbon cycle under conditions of changing climatic and environmental conditions.

The Arctic contains a huge amount of organic carbon (OC) buried inland and within the Arctic Ocean sedimentary basin, that is extremely sensitive to increased global temperatures because of the ice content of both on-land and submarine permafrost. Recent studies show that at present the offshore permafrost (not onshore permafrost) is the most fragile component of the arctic cryosphere (Rachold et al. 2007, Shakhova et al. 2008). The most pronounced warming is currently registered in the East Siberian part of the Arctic, where surface air temperature increased during the 2000–2005 period by about 5°C compared to the 20th century temperature average. It is reasonable to expect that under conditions of continuing warming the regional carbon pool, which consists of OC in Siberian soil and sediments and seabed reservoirs of methane (CH4), will be disturbed and signs of this disturbance will occur over the East Siberian Arctic shelf (ESAS). The ESAS will be employed as an integrator of ongoing changes in surrounding land, creating a terrestrial or exogenous signal which is carried by fresh water (FW), and of in situ changes, creating a marine or endogenous signal, which is generated by submarine permafrost destabilization, increasing coastal erosion, and involvement of old carbon in the modern biogeochemical cycle. Both signals will probably reflect water cycle fluctuations caused by atmospheric circulation pattern shifts. The simple approach described by Shakhova et al. (2005) allowed a quantitative evaluation of the ocean’s environmental changes. This multi-year field campaign (on annual base since 1999) is the first to connect land, shelf, and basin in a study of the regional carbon cycle.

Objectives of these research goals include investigating how redistribution of old carbon from degrading on-land and submarine permafrost and from coastal erosion contributes to the carbon pool of the ESAS; quantifying the contribution of seabed CH4 reservoirs such as hydrates and natural gas to current ESAS CH4 emissions, and how these contributions will increase under continuing warming; defining specific factors which control CH4 emission to the ESAS atmosphere in order to develop a conceptual model of CH4 propagation from the seabed to the atmosphere, and assess the strength of the source in its dynamics; studying how changes in the hydrological cycle of surrounding land and alteration of terrestrial carbon cycles contribute to formation and propagation of halocline waters and affect hydrological and biogeochemical parameters of shelf water masses; and quantifying the area-scaled ESAS contribution of CH4 and CO2 to the atmosphere.

The knowledge gained will be essential for understanding basic mechanisms and factors which determine carbon fluxes into the ESAS (which is the broadest and shallowest shelf), carbon propagation and fate within the shelf area, and the impact of outgoing carbon on the atmosphere and adjacent Arctic Ocean regions. Ongoing environmental change affected marine carbon cycling will be quantified with emphasis on the contribution of seabed CH4 reservoirs such as hydrates and natural gas to current CH4 emissions over the ESAS and Northern Hemisphere, and how these contributions will increase under continuing warming. It will be also shown how system responses to climate change will impact the delivery of terrestrial OC to the Arctic Ocean.