Heave compensation and formation strength evaluation from downhole acceleration measurements while coring

In order to evaluate the efficiency of heave compensation in the Ocean Drilling Program, we developed a device measuring the acceleration of the core barrels. First results show that heave compensation limits bit motion to 10% of the surface heave. We also use the acceleration data to characterize the formation. On rotary corers, acceleration amplitudes decrease with increasing hardness of the formation. Comparison with geophysical logs shows that this relationship can resolve cm-scale features. On piston corers, the maximum acceleration is characteristic of the sediment shear strength. Easy and fast to deploy, this tool allows to characterize formations before any sample analysis.     

Application of the Genetic Algorithm to the Problem of Reconstruction of Missing Data

We study the problem of reconstruction (interpolation and extrapolation) of the vertical profiles of hydrochemical and hydrobiological elements according to incomplete sets of data with simultaneous filtration of short-period components based on expansions in empirical orthogonal functions. The genetic algorithm is used to compute the coefficients of expansion of profiles with missing data. We present the results of processing the data arrays on oxygen, chlorophyll A, and biogenic elements collected in the Black Sea in 1982–1993. The mean error of reconstruction of the profiles enables us to conclude that the proposed method has considerable advantages over the conventional approaches.     

Simulation of seasonal anomalies of atmospheric circulation using coupled atmosphere-ocean model

A coupled atmosphere-ocean model intended for the simulation of coupled circulation at time scales up to a season is developed. The semi-Lagrangian atmospheric general circulation model of the Hydrometeorological Centre of Russia, SLAV, is coupled with the sigma model of ocean general circulation developed at the Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), INMOM. Using this coupled model, numerical experiments on ensemble modeling of the atmosphere and ocean circulation for up to 4 months are carried out using real initial data for all seasons of an annual cycle in 1989–2010. Results of these experiments are compared to the results of the SLAV model with the simple evolution of the sea surface temperature. A comparative analysis of seasonally averaged anomalies of atmospheric circulation shows prospects in applying the coupled model for forecasts. It is shown with the example of the El Niño phenomenon of 1997–1998 that the coupled model forecasts the seasonally averaged anomalies for the period of the nonstationary El Niño phase significantly better.     

Hydrophysical and hydrochemical characteristics of the sea areas adjacent to the estuaries of small rivers of the Russian coast of the Black Sea

This paper presents the results of long-term in situ and satellite measurements at shelf areas adjacent to the estuaries of the small rivers of the Russian coast of the Black Sea (Mezyb, Pshada, Vulan, Tuapse, Bitkha, Sochi, Cudepsta, Mzymta). The quantitative characteristics of the response of the hydrophysical and hydrochemical fields at the sea shelf on the influence of the continental river discharge are presented for each of these areas. A number of indicators of the water quality (the concentrations of the nitrate and nitrite forms of nitrogen, the phosphorus, the silica, the dissolved oxygen, the value of the total alkalinity and pH, the mineral and organic suspended matter, and the chlorophyll a) are considered in the context of the anthropogenic and terrigenous influence. In this paper, the emphasis was placed on the Mzymta River plume at the shelf area adjacent to the city of Sochi, where the measurements were repeatedly performed during the spring flooding conditions in the period from 2007 until 2012. The interannual variability of the water quality indicators and the seasonal and short-term variability of the area and the configuration of the plume, which transports suspended matter and anthropogenic pollution, were considered.     

Long-term moored array measurements of currents and hydrography over Georges Bank: 1994–1999

In conjunction with the GLOBEC (Global Ocean Ecosystems Dynamics) program, measurements of moored currents, temperature and salinity were made during 1994–1999 at locations in 76 m of water along the southern flank of Georges Bank and at the Northeastern Peak. The measurements concentrate on the biologically crucial winter and spring periods, and coverage during the fall is usually poorer.Current time series were completely dominated by the semidiurnal M₂ tidal component, while other tidal species (including the diurnal K₁ component) were also important. There was a substantial wind-driven component of the flow, which was linked, especially during the summer, to regional–scale response patterns. The current response at the Northeast Peak was especially strong in the 3–4 days period band, and this response is shown to be related to an amplifying topographic wave propagating eastward along the northern flank. Monthly mean flows on the southern flank are southwestward throughout the year, but strongest in the summertime. The observed tendency for summertime maximum along-bank flow to occur at depth is rationalized in terms of density gradients associated with a near-surface freshwater tongue wrapping around the Bank.Temperature and salinity time series demonstrate the presence, altogether about 25% of the time, of a number of intruding water masses. These intrusions could last anywhere from a couple days up to about a month. The sources of these intrusions can be broadly classified as the Scotian Shelf (especially during the winter), the Western Gulf of Maine (especially during the summer), and the deeper ocean south of Georges Bank (throughout the year). On longer time scales, the temperature variability is dominated by seasonal temperature changes. During the spring and summer, these changes are balanced by local heating or cooling, but wintertime cooling involves advective lateral transports as well. Salinity variations have weak, if any, seasonal variability, but are dominated by interannual changes that are related to regional- or basin-scale changes.All considered, Georges Bank temperature and salinity characteristics are found to be highly dependent on the surrounding waters, but many questions remain, especially in terms of whether intrusive events leave a sustained impact on Bank waters.     

Late Pleistocene to Holocene sedimentation and hydrocarbon seeps on the continental shelf of a steep,tectonically active margin,southern California,USA

Small, steep, uplifting coastal watersheds are prolific sediment producers that contribute significantly to the global marine sediment budget. This study illustrates how sedimentation evolves in one such system where the continental shelf is largely sediment-starved, with most terrestrial sediment bypassing the shelf in favor of deposition in deeper basins. The Santa Barbara–Ventura coast of southern California, USA, is considered a classic area for the study of active tectonics and of Tertiary and Quaternary climatic evolution, interpretations of which depend upon an understanding of sedimentation patterns. High-resolution seismic-reflection data over >570 km² of this shelf show that sediment production is concentrated in a few drainage basins, with the Ventura and Santa Clara River deltas containing most of the upper Pleistocene to Holocene sediment on the shelf. Away from those deltas, the major factor controlling shelf sedimentation is the interaction of wave energy with coastline geometry. Depocenters containing sediment 5–20 m thick exist opposite broad coastal embayments, whereas relict material (bedrock below a regional unconformity) is exposed at the sea floor in areas of the shelf opposite coastal headlands. Locally, natural hydrocarbon seeps interact with sediment deposition either to produce elevated tar-and-sediment mounds or as gas plumes that hinder sediment settling. As much as 80% of fluvial sediment delivered by the Ventura and Santa Clara Rivers is transported off the shelf (some into the Santa Barbara Basin and some into the Santa Monica Basin via Hueneme Canyon), leaving a shelf with relatively little recent sediment accumulation. Understanding factors that control large-scale sediment dispersal along a rapidly uplifting coast that produces substantial quantities of sediment has implications for interpreting the ancient stratigraphic record of active and transform continental margins, and for inferring the distribution of hydrocarbon resources in relict shelf deposits.     

Large bio-geographical shifts in the north-eastern Atlantic Ocean: From the subpolar gyre, via plankton, to blue whiting and pilot whales

Pronounced changes in fauna, extending from the English Channel in the south to the Barents Sea in the north-east and off Greenland in the north-west, have occurred in the late 1920s, the late 1960s and again in the late 1990s. We attribute these events to exchanges of subarctic and subtropical water masses in the north-eastern North Atlantic Ocean, associated with changes in the strength and extent of the subpolar gyre. These exchanges lead to variations in the influence exerted by the subarctic or Lusitanian biomes on the intermediate faunistic zone in the north-eastern Atlantic. This strong and persistent bottom-up bio-physical link is demonstrated using a numerical ocean general circulation model and data on four trophically connected levels in the food chain – phytoplankton, zooplankton, blue whiting, and pilot whales. The plankton data give a unique basin-scale depiction of these changes, and a long pilot whale record from the Faroe Islands offers an exceptional temporal perspective over three centuries. Recent advances in simulating the dynamics of the subpolar gyre suggests a potential for predicting the distribution of the main faunistic zones in the north-eastern Atlantic a few years into the future, which might facilitate a more rational management of the commercially important fisheries in this region.     

A cross-ecosystem comparison of spatial and temporal patterns of covariation in the recruitment of functionally analogous fish stocks

Temporal and spatial patterns of recruitment (R) and spawning stock biomass (S) variability were compared among functionally analogous species and similar feeding guilds from six marine ecosystems. Data were aggregated into four regions including the Gulf of Maine/Georges Bank, the Norwegian/Barents Seas, the eastern Bering Sea, and the Gulf of Alaska. Variability was characterized by calculating coefficients of variation and anomalies for three response variables: ln(R), ln(R/S), and stock–recruit model residuals. Patterns of synchrony and asynchrony in the response variables were examined among and between ecosystems, between- and within-ocean basins and among functionally analogous species groups using pair-wise correlation analysis corrected for within-time series autocorrelation, multivariate cross-correlation analyses and regime shift detectors. Time series trends in response variables showed consistent within basin similarities and consistent and coherent differences between the Atlantic and Pacific basin ecosystems. Regime shift detection algorithms identified two broad-scale regime shift time periods for the pelagic feeding guild (1972–1976 and 1999–2002) and possibly one for the benthic feeding guild (1999–2002). No spatial patterns in response variable coefficients of variation were observed. Results from multivariate cross-correlation analysis showed similar trends. The data suggest common external factors act in synchrony on stocks within ocean basins but temporal stock patterns, often of the same species or functional group, between basins change in opposition to each other. Basin-scale results (similar within but different between) suggest that the two geographically broad areas are connected by unknown mechanisms that, depending on the year, may influence the two basins in opposite ways. This work demonstrates that commonalities and synchronies in recruitment fluctuations can be found across geographically distant ecosystems but biophysical causes of the fluctuations remain difficult to identify.