Vadim Paka

Environmental Hazards of Sea-Dumped Chemical Weapons

Does the post-WWII burial at sea of chemical weapons still pose a human and environmental risk?

Generation of subsurface cyclonic eddies in the southeast Baltic Sea: Observations and numerical experiments

[1] Closely spaced CTD transects performed in the summertime reveal simultaneous downward/upward bendings of temperature/salinity contours in the seasonal thermocline/ permanent halocline of the Stolpe Channel and the Gulf of Gdansk, which may be interpreted as geostrophically balanced cyclonic eddies in the intermediate layer. To examine processes capable of forming the observed cyclonic eddies, a numerical simulation based on the Princeton Ocean Model (POM) has been initiated. The subsurface cyclones in the Stolpe Channel were satisfactory simulated in model runs under easterly/ northerly wind conditions. Their formation was shown to result from the adjustment of the high potential vorticity (PV) outflow (from the Bornholm Basin via the Stolpe Sill) to low potential vorticity environment by vortex stretching (so-called the PV outflow hypothesis by Spall and Price [1998]). In accordance with the real wind conditions, a cyclonic eddy observed in the intermediate layer of the Gulf of Gdansk was satisfactorily reproduced in a model run with the westerly wind shutdown, which implies westward transport throughout the Stolpe Channel and thereby excludes the PV outflow hypothesis. The subsurface cyclone simulated in the Gulf of Gdansk was traced to form in the course of relaxation of the coastal downwelling baroclinic jet.

Generation of cyclonic eddies in the Eastern Gotland Basin of the Baltic Sea following dense water inflows: numerical experiments

Abstract A sigma ( σ )-coordinate ocean model by Blumberg and Mellor (POM) is applied to study the formation processes of mesoscale cyclones observed in the Eastern Gotland Basin following the dense water inflows. The initial conditions simulate a situation when the Arkona and Bornholm basins and partially the Slupsk Furrow are already filled with the inflow water of the North Sea origin, while the Eastern Gotland and Gdansk basins still contain the old water of pre-inflow stratification. Model runs with constant and time-dependent winds, changing the buoyancy forcing, grid geometry and bottom topography display the following. Entering the Eastern Gotland Basin from the Slupsk Furrow, the bottom intrusion of saline inflow water splits in two: one goes northeast towards the Gotland Deep, and second moves southeast towards the Gulf of Gdansk. An intensive mesoscale cyclonic eddy carrying the inflow water is generated just east of the Slupsk Furrow with the inflow pulse. A number of smaller cyclones with boluses of the inflow water are formed in the permanent halocline along the saline intrusion pathway to the Gotland Deep. Following Spall and Price [J. Phys. Oceanogr. 28 (1998) 1598], the cyclones are suggested to form by the adjustment of the high potential vorticity inflow water column to a low potential vorticity environment.

What drives thermohaline intrusions in the Baltic Sea

Abstract Using data from closely spaced CTD profiles taken after the 1993 major inflow of North Sea water, we investigate the characteristics and generation mechanisms of finestructure intrusions in the Baltic halocline. Due to the strong prevalence of salinity over temperature in density stratification, the salt fingering is not possible, and diffusive convection has a limited effect on thermohaline intrusions in the halocline. Some evidence for inertial oscillations as a driving mechanism for the intrusions is found. In several occasions, we observed odd intrusion-like structures crossing isopycnals in such a way that the along-layer density ratio is approximately equal to the vertical density ratio. We show that these ‘odd intrusions’ are not likely to be generated from the interleaving process, and several alternate scenarios for their generation are suggested.

Internal solitons in the sea: Experimental data

Results of two comprehensive internal wave experiments carried out at the shelf edge in the mid-atlantic bight (JUSREX-92 and SWARM-95) are analyzed. Evidence of soliton features of the observed intense internal waves are discussed with special attention to the propagation speed and amplitude dispersion of solitons. A method for estimation of phase velocity of internal waves by analysis of time/depth variations of three current velocity components is proposed. Specific distortion of the orbital velocity field in internal waves propagating against the background shear current is discussed (ldquoshear contaminationrdquo effect).

Estimates of eddy diffusivity in bottom boundary layer of the Bornholm Deep

Reliable estimate of eddy diffusivity in the bottom boundary layer (BBL) of the Bornholm Deep is the issue of practical importance because it would control dispersion of the chemical warfare agents dumped in the Deep after WW II [Helcom, 1994]. The most common way to arrive at an estimate of the eddy diffusivity, K is to apply a well-known parameterization of mixing in the Baltic halocline due to internal wave instability suggested by [A. Stigebrandt, 1987] K = min(K_max, alpha/N), where K_max is the maximum value of K, N is the buoyancy frequency, and alpha =1times10^-7 m² s^-2 [H.E.M. Meier, 2007] or alpha = 0.87times10^-7 m² s^-2 [H.-U. Lass, 2003] is the empirical constant. Taking N_BBL =0.02 s^-1 for near-bottom layer and N_halocline =0.03 s^-1 for the halocline in the Bornholm Deep [J. Elken, 1996] one obtains K_BBL= 0.5times10^-5 m² s^-1 and K_halocline = 0.33times10^-5 m² s^-1. However, the above estimate of K_BBL does not take into account the possibility of enhancement of eddy diffusivity in BBL due shear instability of the near-bottom current and a variety of mechanisms of boundary mixing [J.H. Reissmann, 2007]. Numerical simulations based on the Princeton Ocean Model with a second and a half moment turbulence closure by Mellor and Yamada [1982] embedded brought for eddy diffusivity in the Bornholm Deep BBL and the BBL thickness the values of K_BBL1= 2.5times10^-4 m² s^-1 and h_BBL1 = 2 m respectively. Eddy diffusivity in the Bornholm Deep BBL can be also estimated using data of tow-yo CTD profiling in a near-bottom layer performed aboard R/V Shelf in Summer 2006.

Best Practices in Monitoring

This chapter summarizes the methods used within the MODUM project for monitoring chemical munition dumpsites. It includes general introduction to monitoring process, listing the requirements that are a basis for the establishment of full scale monitoring programme. It describes survey procedures, for locating dumped munitions, Sampling and analytical procedures for the detection of Chemical Warfare Agents, as well as the usage of fish as bioindicators are described. Modelling of pollutants originating from dumped munitions is presented and discussed. Only methods, which were proven to be most effective within the MODUM projects were selected, also data interpretation methods providing coherent information regarding the environmental risk are explained in details.

Sustainable management of oil polluting wrecks and chemical munitions dump sites

Dumped chemical weapons that are corroding and exposed to the marine environment can cause contamination and health risks for marine fauna and humans. This paper describes some of the work that is done in the EU-DAIMON (Decision Aid for Marine Munitions) project including the development of a decision support method and previous field results that indicate that bottom trawling re-suspend sediments and spread contaminants and that recently caught fish at the Maseskar dump site contains detectable concentrations of chemical weapons from World War II.

On horizontal and vertical transport of Ford water

Abstract Three transects of shelf-origin water (Ford water) at the slope water — Gulf Stream boundary between 69 °30′W and 72 °10′W (August 1–5, 1992) were run with a towed scanning profiler equipped with conductivity-temperature-depth probe. The sections from the surface to 200 m depth with horizontal resolution of about 1 km demonstrate simultaneous propagation of the surface and subsurface Ford water connected by a thin and narrow (several km wide) transition area. The thermohaline structure and sharp density fronts at the former water boundaries are maintained downstream. Transport is estimated at 460 ∗ 10 3 m 3 / s (with 33% of shelf water, whose salinity is taken to be 32%.) that is 4.6 times greater than a previous estimate. It is suggested that evidence is found of intermittent vertical transport of freshened water from the surface band to the subsurface one. The subsurface band separates in two features in the transition area from predominent thermoclinicity of the Gulf Stream front to its noticeable baroclinicity owing to the increasing slope of the isopycnal ≅ 26σ t , the lower feature being subducted along the property front to a local depth of the isopycnal bounding the feature from below. Thermohaline intrusion of the freshened water in the Gulf Stream thermocline in the same transition area provides cross-frontal transport of the water, a trace of which is found in the Gulf Stream water at a depth of ≅ 190 m. The association of formation of the intrusion, whose axis is inclined to isopycnal surfaces, with thermohaline parameters of the front and ageostrophic circulation at the site of its cyclonic curvature due to a spin-off eddy is discussed.