ENVIROMIS – 2016 Tomsk, July , 11-16 Study of the impact of atmospheric forcing and river discharge on the Laptev Seav summer hydrography and submarine permafrost state E.Golubeva, G.Platov, V.Malakhova, D.Iakshina and M.Krayneva Russian Academy of Sciences Novosibirsk Scientific Centre Institute of Computational Mathematics and Mathematical Geophysics SB RAS
Plan of presentation • Region of East Siberian Arctic Shelf. Motivation of investigation • Observational data and analysis results • Method of numerical modeling • Numerical results • One of the important unresolved problems • Conclusion
The Eastern Siberian Arctic Shelf (ESAS), including the Laptev and East Siberian Seas is the shallowest (20-30m average depth) and broadest (400-8000 km from shoreline) shelf region of the World Ocean
rivers The vast Siberian Shelf regions cover more than one third of the total Arctic Ocean area, and receive freshwater from several large rivers, with 394 km3 yr_1 from the Ob River (RosHydromet gauge data at Salekhard, from 1930to 1999) and 580 km3 yr_1 from the Yenisey River (RosHydromet gauge data at Igarka, from 1936 to 1999) in the Kara Sea, and about 541 km3 yr_1 from the Lena River (RosHydromet gauge data at Kusur, from 1985 to 2007) in the Laptev Sea (Fig. 1). (RosHydromet gauge data are accessible at http://www.r-Arcticnet.sr.unh.edu through the Regional, Eletronic Hydrographic Data Network for the Arctic Region.)
Satellite data reveal how the new record low Arctic sea ice extent, from Sept. 16, 2012, compares to the average minimum extent over the past 30 years (in yellow). Sea ice extent maps are derived from data captured by the Scanning Multichannel Microwave Radiometer aboard NASA's Nimbus-7 satellite and the Special Sensor Microwave Imager on multiple satellites from the Defense Meteorological Satellite Program. Credit: NASA/Goddard Scientific Visualization Studio
The Northern Sea Route comprises all routes from the Barents to the Chukchi Sea and the Bering Strait suitable for shipping and includes Arctic seas and part of the Arctic Ocean limited by Russian economic zone http://rusinform.net/severnyj-morskoj-put
Time series of annual atmosphere temperature anomaly East Siberian sector of the Arctic shelf -is the region where climatic changes of recent decades are the most pronounced. Recently it was reported about increasing coastal erosion rates Photo by M.Grigoriev
Dissolved methane in the Laptev Sea ans East-Siberian Sea. Observational data 2004 2003 Distribution of dissolved methane in the surface layer (a), and bottom layer (b) (Shakhova and Semiletov, 2006). The essential increasing of the dissolved methane concentration during 2003-2005 years. Surface layer maximum: 2003 - 30nM, 2004 - 115 nM, 2005 - 500nM Bottom layer: 2003 - 87nM, 2004 - 154 nM, 2005 - 220nM The extreme methane anomalies in plume areas indicate the presence of both surface and 2005 bottom methane sources, which might reflect unique geological, hydrological and climatic factors
The data coverage of the interpolated field (percentage from the entire subregionarea) within subregions 1–7 for (b) winter (February–April) and (c) summer (July–September) Dmitrenko, I. A., S. A. Kirillov, L. B. Tremblay, H. Kassens, O. A. Anisimov, S. A. Lavrov, S. O. Razumov, and M. N. Grigoriev (2011), J. Geophys. Res., 116, C10027, doi:10.1029/2011JC007218.
J. Geophys. Res., 116, C10027, doi:10.1029/2011JC007218.
Weingartner T.J., Sasaki Y., Pavlov V.K. and Kulakov M.Yu. The Siberian Coastal Current: A wind and buoyancy-forced Arctic coastal current // J. of Geoph. Res. 1999. Vol. 104, C12. P. 29,697–29,713.
D. Bauch, 1 I. A. Dmitrenko, 1 C. Wegner, 1 J. Ho¨ lemann, 2 S. A. Kirillov, 3 L. A. Timokhov, 3 and H. Kassens 1 JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, C05008, doi:10.1029/2008JC005062, 2009 Figure 1. Temperature and salinity data on sections along 130E for summers (a) 1994 and (b) 1999. Schematic drawings indicate the supposed water circulation during years with ‘‘onshore’’ and ‘‘offshore’’ atmospheric forcing. The flow of the river plume is from west to east in 1994 as indicated by the arrow;
Two main circulation modes in the Arctic Ocean Cyclonic mode Anticyclinic mode
The vorticity index defined by Walsh et al. (1996) has been used to characterize the atmospheric forcing on the Laptev Sea surface waters basin (Dmitrenko et al. 2005). Another index based on the simple Ekman trajectory model for surface Lagrangian particles has been used in (Bauch et al 2011) to investigate the effect of near surface winds on the river water summer distribution. In Bauch et al.,2011 it was found that the third EOF pattern represents the relevant mode of variability, which determines local wind and SLP fields, and thus the distribution of river water on the Laptev Shelf, whereas the first and second EOFs are only of minor importance. Comparison between our normalized trajectory index calculated from model results with 3% (light green) and 7% (dark green) atmospheric wind forcing and the vorticity index (red line; inverted values)..
Dorothea Bauch 1 , Matthias Gro¨ ger 2 , Igor Dmitrenko 1 , Jens Ho¨ lemann 3 , Sergey Kirillov 4 ,Andreas Mackensen 3 , Ekatarina Taldenkova 5 & Nils Andersen 6 Citation: Polar Research 2011, 30: 5858 - DOI: 10.3402/polar.v30i0.5858
Sea level pressure (NCEP/NCAR data), EOF and PC, summer (jja)
Numerical Modeling
Coupled Ice-Ocean Model 3D Ocean Circulation Model of ICMMG based on z-level vertical coordinate approach (Kuzin1982, Golubeva at al.,1992, Golubeva,[2001,2008], Golubeva and Platov,[2007]) • Conservation laws for heat, salt and momentum with Boussinesq, hydrostatic and ‘rigid lid’ approximations • Separation of the external and internal mode in momentum equations • Barotropic momentum equations are expressed in term of stream function • QUICKEST (Leonard,[1992]) is used in the latest model version for the T-S advection. • Two versions of mixed layer parameterization: - Vertical adjustment based on the Richardson number - Vertical diffusion coefficient based on the stable solution of turbulent energy equation 14-19км Ice model-CICE 3.0 (elastic-viscous-plastic) 38 vertical levels W.D.Hibler ,1979, E.C.Hunke, J.K.Dukowicz,1997, G.A.Maykut 1971 C.M.Bitz, W.H.Lipscomb 1999,J.K.Dukowicz, J.R.Baumgardner 2000, W.H.Lipscomb, E.C.Hunke 2004
Platov G.A. et al., Bulletin ICMMG,2015
During the anticyclonic The results of the 3D modeling present the circulation the salinity spatial-temporal variability of the summer front is oriented according hydrological fields on the Siberian shelf to the prevailing wind offshore field, and can shift to the north-east or north-west. An intensive northward flow in the central part of the sea provides a fresh water transport towards the edge of the shelf zone. The eastward flow is steadily presented during the cyclonic atmospheric circulation. The salinity front develops in surface waters and spreads along the coast of the onshore Laptev and East Siberian Seas.
offshore onshore
In contrast to the studies of the salinity distribution in the Arctic shelf waters, due to the influence of the river runoff, minor attention has been paid to the issue associated with the study of the role of the heat coming from the river waters.
The primary effect from the river heat flux could be seen in the state of the sea ice. The most important difference between the two experiments was obtained in the region of the Lena River Delta. The results simulated show a decrease in the ice thickness caused by river heat in the vicinity of the Lena River Delta in spring and in summer. In June, the heat coming with the river water results in the ice melting in the immediate vicinity of the river. June July Ice thickness difference caused by Lena River heat flux in numerical experiment
Averaged temperature anomalies . Run2 (rivers heat flux) - Run1 (no river heat flux)
Nested Laptev Sea Regional Model ► POM, Laptev Sea region,nested into ICMMG AO-NA model ► Horizotnal grid 200м-20км, ► Modeling period- up to 1 year 27
Model temperature
onshore onshore offshore offshore Salinity Temperature June July Aug Sept 2007 2008 2007 2008
In contrast to Region I and Region II, the temperature anomaly in Region III has some peculiarities. Almost regularly the surface layer has two small local maxima, the first maximum is observed in June and the second - in August. The first maximum is defined by the Yana River heat flux, and the second one is resulted from the Lena River water reaching Region III.
Transgressions and regressions of the ocean, which occurred in the past, have affected the development of permafrost on the Arctic shelf. The duration of the transgression/regression cycle, air temperature, the ocean bottom water temperature, the geothermal heat flux are some of the most important factors affecting the subsea permafrost distribution a b Simulated present-day permafrost (in m) for a heat flow of 60 mW/m 2 : (a) the permafrost thickness in the ESAS, (b) simulated locations of permafrost upper boundary in the ESAS for 2012, (c) deepening of a permafrost upper boundary from 1948 to 2012 in the ESAS
Recommend
More recommend
