On the vertical structure of temperature anomalies in the North Atlantic

The expansion of the temperature anomaly field in the North Atlantic is considered using natural orthogonal functions of depth. It is shown that the first few components of this expansion describe the field both at the surface and in the upper 1000 m layer accurately enough. The relation between the water temperature anomaly at some levels and the above components is estimated for various regions of the ocean.Translated by Mikhail M. Trufanov.     

Errors in recent ocean tide models: possible origin and cause

Recently, the TOPEX/POSEIDON Science Working Team has recommended the FES95.2.1 and CSR3.0 ocean tide models for reprocessing the TOPEX/POSEIDON Geophysical Data Records. Without doubt, the performance of these models, especially in the deep oceans, is excellent. However, from a comparison of these hydrodynamically consistent models with the purely empirical DW3.2 and DEOS96.1 models, it appears that FES95.2.1 and CSR3.0 are affected by basin boundary related errors which are caused by the basin-wise solution procedure of the FES ocean tide model series. In their turn, the empirical DW3.2 and DEOS96.1 models seem to suffer from significant errors in the Antarctic seas due to the seasonal growth and decay of Antarctic sea ice. Also, bathymetry-induced differences were found between the hydrodynamically consistent models and the empirical models. Concerning these differences, TOPEX/POSEIDON and ERS-1 crossover statistics unfortunately do not provide conclusive results on which models are in error.     

Comparison between zooplankton data collected by the Continuous Plankton Recorder survey in the English Channel and by WP-2 nets at station L4, Plymouth (UK)

Zooplankton sampling has been carried out by the Continuous Plankton Recorder (CPR) survey since the 1930s enabling the study of long-term changes in plankton populations, the elucidation of seasonal patterns of abundance, and more recently providing zooplankton biomass estimates for ecosystem models. Data for zooplankton abundance collected by CPR tows in the Western English Channel (between 1988 and 1998) were compared to vertically integrated samples collected from station L4 off Plymouth, UK. Comparisons were made for locally abundant copepods (including Acartia, Calanus, Para/Pseudocalanus, Centropages, Oithona and Temora) collected by CPR and WP-2 nets. All dominant species recorded at L4 were also common to the CPR data. However, the position of the taxa in the two datasets was not equivalent. Seasonal cycles revealed by CPR data were significantly similar to those recorded throughout the water column at L4 for most taxa. However, absolute levels of abundance differed for the two datasets: abundances were underestimated by CPR samples when compared to those of vertically integrated samples by a factor of between 2 and 35, with the exception of Centropages. The differing mesh sizes (200 and 270 μm) of the WP-2 net and CPR mesh could only partially explain these differences in abundance, implying that the behaviour of individual taxa and their depth in the water column also influenced the abundance recorded.     

Hydrothermal Vent Geology and Biology at Earth’s Fastest Spreading Rates

Earth’s fastest present seafloor spreading occurs along the East Pacific Rise near 31°–32° S. Two of the major hydrothermal plume areas discovered during a 1998 multidisciplinary geophysical/hydrothermal investigation of these mid-ocean ridge axes were explored during a 1999 Alvin expedition. Both occur in recently eruptive areas where shallow collapse structures mark the neovolcanic axis. The 31° S vent area occurs in a broad linear zone of collapses and fractures coalescing into an axial summit trough. The 32° S vent area has been volcanically repaved by a more recent eruption, with non-linear collapses that have not yet coalesced. Both sites occur in highly inflated areas, near local inflation peaks, which is the best segment-scale predictor of hydrothermal activity at these superfast spreading rates (150 mm/yr).     

Experimental research on the hydrophysical characteristics and dynamics of waters in the north-west Black Sea in the region of the main Black Sea current

The results of measurements of hydrophysical parameters in the upper layer of the sea at an observation site located south-west of the Crimea are reported. The current pattern, the distribution of the upwelling and downwelling zones at the observation site, and the location of the mesoscale fronts are discussed.Translated by Mikhail M. Trufanov.     

The choice of a dynamico-stochastic model for ocean monitoring — A compromise between the accuracy and cost of computations

In this paper we compare, two dynamico-stochastic models (DSMs) with different hydrodynamic parts, designed to study a large-scale North Atlantic region. As a performance criterion, RMS errors (over the horizon) in density and velocity field reconstruction are used. It has been shown that in some cases it seems rational to use DSMs with simplified hydrodynamic parts. This helps to expedite the computations and to reduce the related costs without much detriment to the quality of hydrophysical field simulation.UDK 551.465.001.573(261.1).Translated by Vladimir A. Puchkin.     

Contaminant concentrations and toxicity of sea-surface microlayer near Los Angeles, California

Sea-surface microlayer samples were collected from six nearshore areas receiving different amounts of anthropogenic inputs. The samples were analyzed for selected trace metals, chlorinated hydrocarbons, and polycyclic aromatic hydrocarbons. The relative toxicities of the samples were determined with fish embryo bioassays.Contaminant concentrations generally increased from offshore to the inshore stations. Contaminant concentrations were several orders of magnitude higher in microlayer samples from the highly industrialized Los Angeles and Long Beach harbors compared to samples from a site 15km offshore. Microlayer samples from the inshore stations were significantly more toxic, and induced significantly more developmental abnormalities and chromosome aberrations, than samples from the offshore stations.