RESEARCH HIGHLIGHT

Linking terrestrial and marine measurements in the Lena-Laptev Sea system

September 28, 2006

The Arctic region is linked with the rest of planet Earth via carbon and freshwater cycles (SEARCH, 2005). However, our knowledge of the processes driving the Arctic system today is still very limited, thus making it difficult to predict future climate scenarios. In this context the Lena River-Laptev Sea system is of particular interest. The carbon complex study there has a high priority at IARC.

This is the first time that we are working on linking marine and terrestrial measurements of methane(CH₄) and carbon dioxide (CO₂) to study their fluxes across the air-water interfaces. We  also study the transport and fate of terrestrial organic carbon (dissolved and particulate carbon) from the Lena river and eroded coastal ice complexes. Those data are essential to establish a model for carbon cycling in the Arctic atmosphere-land-shelf system. This study is a continuation of  the joint Russia-US Arctic studies organized and accomplished by our group in summer of 2003, 2004, 2005 (Semiletov et al., 2006; Shakhova et al., 2006).

Since our departure from Vladivostok on August 30th we spent three days in the Amoursky region because due to air flight logistics. Our joint IARC-POI FEBRAS (Pacific Oceanological Institute, Far-Eastern Branch of Russian Academy of Sciences) scientific team reached Tiksi in the late evening of  the September 3rd. Since that time the air temperature dropped to -5 degrees C winds usually ranged between 10-20m per second.

On September 5th, we started measurements in the Lena Delta-Laptev Sea near shore zone (Figure 1). In total, 72 stations were accomplished.

Figure 1. The study area served during the Lena-Laptev Sea near shore study.

We established turbulent CO₂ and CH₄ flux measurements above sea and fresh water (Lena channels) surfaces. Eddy correlation technique was utilized using the 3D sonic anemometer, LiCor-7500 and DLT-100 sensors (Figure 2).  Dynamics of the dissolved CH₄  and carbonate system in the river-sea was measured using head space and pH-TAlk techniques. Particulate material (PM) was sampled using ultra-filtration technique.  Hydrological  CTD (conductivity-temperature-depth) probe Seabird 19+ probe was equipped with optical sensors to measure turbidity and colored dissolved organic material (CDOM). Based on the data obtained in the previous Russia-US cruises in the Laptev and East-Siberian seas (2003-2005) we found a stable and high regional correlation between turbidity and PM concentration, CDOM and concentration of dissolved organic carbon. New data will be used to learn more about fluvial export and dynamics of terrestrial carbon.

Figure 2. Shipboard micrometeorological equipment.

Sediment input to the Arctic shelf resulting from erosion of ice-rich, permafrost-dominated coastlines (Figures 3, 4) may be equal to or greater than or equal to input from river discharge. To estimate the amount of sediments and organic carbon derived from coastal erosion we established the CO₂ flux measurements and sediment sampling across the ice-complex-sea interface (Figure 5, 6).

Figure 3. Coastal dynamics as a function of environmental forcing, coastal morphology, and onshore and offshore permafrost characteristics (http://www.awi-potsdam.de).

Figure 4. In summer 2006 the rate of coastal erosion at Muostakh island reached >10m

Figure 5. Chamber flux measurements in the near shore zone: onshore ice-complex, Muostakh Island.

Figure 6. Chamber flux measurements in the nearshore zone: offshore ice-complex, Muostakh Island.

Tomorrow we plan to commence an offshore helicopter survey using fast methane analyzer DLT-100 and carbon dioxide analyzer. A MI-8 helicopter will be used (total distance above the Laptev Sea ~1,300km).

The marine activity will continue in the Laptev Sea and along the Northern Sea Route.  We expect to accomplish the field research in the early October.

~ Dr. Igor Semiletov and Dr. Natalia Shakhova (IARC)

References

1. Semiletov, I., I.I. Pipko, I.A. Repina, Shakhova N. 2006. Carbonate dynamics and carbon dioxide fluxes across the atmosphere-ice-water interfaces in the Arctic Ocean Pacific sector of the Arctic, Journal of Marine Systems, in press (MARSYS 1224).
2. Shakhova, N., I. Semiletov. 2006.  Methane release and coastal environment in the East Siberian Arctic shelf, Journal of Marine Systems, in press (MARSYS 1223).