Interannual variability of thermal state of the cold subsurface layer in the Okhotsk Sea

Long-term variability of the cold subsurface water (CSW) in the Okhotsk Sea is analyzed on the base of all available oceanographic data collected in March through August of 1946-2015 (total 65,742 stations). The Integral Heat Content (IHC) is calculated for each station and average annual IHC anomalies of the cold subsurface water are determined by month and by 2-degree grid. The IHC anomaly series are analyzed using the EOF analysis. Cycles with period of approximately 30 years are revealed in the variations of the subsurface layer heat content. Thus, in the 1946-1950, its temperature decreased, but it grew since 2009-2010 to 2015. The warming of CSW was also observed in the 1951-1964 and 1978-1994, while the cooling was in the 1965-1977 and 1995-2008. Based on this criterion, the CSW thermal condition in certain years is classified as «extremely cold» in 2001, as «cold» in 1949, 1950, 1951, 1958, 1959, 1960, 1966, 1967, 1969, 1973, 1976, 1977, 1978, 1980, 1999, 2000, 2010, 2012, as «normal» in 1946, 1952, 1953, 1954, 1955, 1957, 1961, 1962, 1965, 1970, 1971, 1972, 1975, 1979, 1982, 1983, 1985, 1986, 1988, 1989, 1990, 1993, 1995, 1996, 1998, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2013, 2014, as «warm» in 1948, 1956, 1964, 1968, 1974, 1981, 1984, 1987, 1991, 1992, 1994, 1997, 2015, and as «extremely warm» in 1963. Statistically significant correlation is found between changes of the CSW thermal conditions and long-term variations of atmosphere and ocean climate indices, as well as local patterns of the atmosphere-ice-ocean interaction in the Okhotsk Sea and adjacent onshore and offshore areas of Asia and the Pacific Ocean

Properties of cores of the water masses in the Okhotsk Sea

Spatial distribution of depth and water properties (temperature, salinity, dissolved oxygen content) are considered in detail for cores of the Okhotsk Sea water masses: subsurface, intermediate, and deep, on the base of the most comprehensive oceanographic data set

Dynamic Topography of the Bering Sea

A new mean dynamic topography (MDT) for the Bering Sea is presented. The product is obtained by combining historical oceanographic and atmospheric observations with high-resolution model dynamics in the framework of a variational technique. Eighty percent of the ocean data underlying the MDT were obtained during the last 25 years and include hydrographic profiles, surface drifter trajectories, and in situ velocity observations that were combined with National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) atmospheric climatology. The new MDT quantifies surface geostrophic circulation in the Bering Sea with a formal accuracy of 2-4 cm/s. The corresponding sea surface height (SSH) errors are estimated by inverting the Hessian matrix in the subspace spanned by the leading modes of SSH variability observed from satellites. Comparison with similar products based on in situ observations, satellite gravity, and altimetry shows that the new MDT is in better agreement with independent velocity observations by Argo drifters and moorings. Assimilation of the satellite altimetry data referenced to the new MDT allows better reconstruction of regional circulations in the Bering Sea. Comparisons also indicate that MDT estimates derived from the latest Gravity Recovery and Climate Experiment geoid model have more in common with the presented sea surface topography than with the MDTs based on earlier versions of the geoid. The presented MDT will increase the accuracy of calculations of the satellite altimeter absolute heights and geostrophic surface currents and may also contribute to improving the precision in estimating the geoid in the Bering Sea

Observing System Simulation Experiments and Adjoint Sensitivity Analysis: Methods for Observational Programs in the Arctic Ocean

Over recent decades, the Arctic Ocean (AO) has experienced profound climate changes. To study these climate changes, several regional observational programs have been started. Because of complicated logistics and remoteness, in situ observations in the AO are extremely expensive. Therefore, an efficient ocean observational system in the AO is critical to understand environmental changes in the Arctic. Observing System Simulation Experiments (OSSEs) and Adjoint Sensitivity Analysis (ASA) are powerful tools that could be used in the optimization of existing and incoming observational programs in the AO. These optimal planning tools recommended by the Study of Environmental Arctic Change (SEARCH) implementation plan, and widely used in atmospheric research, are still rarely implemented in physical and biological oceanography. We provide several examples of how the OSSE and ASA can be used to optimize the locations of high frequency radars and biological tracer surveys and leveraged toward creating an inexpensive drifter observational program capable of providing sufficient information to reconstruct the circulation in the northern Bering, Chukchi, and southern Beaufort Seas.Ces dernières décennies, l’océan Arctique (OA) a connu des changements climatiques d’envergure. Plusieurs programmes d’observation régionaux ont été mis en oeuvre pour étudier ces changements climatiques. En raison de la complexité de la logistique et de l’éloignement, les observations sur place dans l’OA coûtent extrêmement cher. Par conséquent, un système efficace d’observation des océans dans l’OA s’impose pour comprendre les changements environnementaux qui se produisent dans l’Arctique. Les observations expérimentales (Observing System Simulation Experiments, ou OSSE) et la méthode adjointe d’analyse de sensibilité (Adjoint Sensitivity Analysis, ou ASA) sont d’importants outils susceptibles d’être utilisés dans l’optimisation des programmes d’observation actuels et futurs dans l’OA. Ces outils de planification optimaux sont recommandés par le plan de mise en oeuvre de l’étude sur le changement environnemental dans l’Arctique (Study of Environmental Arctic Change, ou SEARCH) et sont largement utilisés dans la recherche atmosphérique, bien qu’ils soient encore rarement employés en océanographie physique et biologique. Nous fournissons plusieurs exemples de la façon dont les OSSE et l’ASA peuvent permettre d’optimiser l’emplacement des radars à haute fréquence et des levés de traceurs biologiques. De plus, elles peuvent stimuler la création d’un programme d’observation de bouées dérivantes peu coûteux pouvant fournir suffisamment d’information pour la reconstruction de la circulation dans les mers de Béring et des Tchouktches au nord, et dans la mer de Beaufort au sud

Microstructure and properties of a silicon coating deposited on a titanium nickelide substrate using molecular-beam epitaxy equipment

The microstructure and properties of a silicon coating on a titanium nickelide substrate were studied to assess the possibility of using such a coating to improve the biocompatibility of medical implants. The silicon coating with thickness of 4.0±0.5 microns was applied to the TiNi substrate on a molecular beam epitaxy unit. The coating had a submicrocrystalline structure with a crystallite size of 0.1...0.2 microns, a developed surface, and high crack resistance

Signal invariance and trajectory steering problem for an autonomous wheeled robot

We give a new convenient parametrization of linear controllers that solve the problem of signal invariance (or disturbance cancellation) for MIMO plants. As an example of application of the obtained results we consider the trajectory tracking problem for non-holonomic wheeled transport robots

Methodology for the Practical Implementation of Monitoring Temperature Conditions over Vast Sea Areas Using Acoustic Thermometry

The methodological and technical possibilities of monitoring temperature fields in the Sea of Japan by acoustic thermometry methods are presented. The proposed tomographic method for monitoring the dynamics and structure of water is based on the transmission and reception of complex phase-shift keyed acoustic signals on a diagnosed track with the determination of the travel time along various ray trajectories, followed by the sound speed (temperature) determination. The physical prerequisites for the practical implementation of thermometric studies at large distances are based on the acoustic “mudslide” effect—the phenomenon of the acoustic energy “injection“ from the near-bottom shelf area to the underwater sound channel of the deep ocean. Based on the Sea of Japan example, an acoustic thermometry system based on tomographic schemes with mobile and stationary hydroacoustic sources for promising work in the field of oceanic climatology is proposed. For numerical calculations of the signal propagation channels’ impulse responses between sources and receivers, a specialized database of oceanological information was formed for the northwestern part of the Sea of Japan. The database includes all available data from organizations in Russia, Japan, North Korea, the Republic of Korea, and the United States (23,247 stations completed from 1925 to 2017). In the example of the Sea of Japan, a high-precision acoustic thermometry system based on tomographic schemes with developed mobile and stationary hydroacoustic transmitting and receiving systems was proposed and experimentally tested

Variability of the Bering Sea Circulation in the Period 1992-2010

Sea surface height anomalies observed by satellites in 1992-2010 are combined with monthly climatologies of temperature and salinity to estimate circulation in the southern Bering Sea. The estimated surface and deep currents are consistent with independent velocity observations by surface drifters and Argo floats parked at 1,000 m. Analysis reveals 1-3-Sv interannual transport variations of the major currents with typical intra-annual variability of 3-7 Sv. On the seasonal scale, the Alaskan Stream transport is well correlated with the Kamchatka (0.81), Near Strait (0.53) and the Bering Slope (0.37) currents. Lagged correlations reveal a gradual increase of the time the lags between the transports of the Alaskan Stream, the Bering Slope Current and the Kamchatka Current, supporting the concept that the Bering Sea basin is ventilated by the waters carried by the Alaskan Stream south of the Aleutian Arc and by the flow through the Near Strait. Correlations of the Bering Sea currents with the Bering Strait transport are dominated by the seasonal cycle. On the interannual time scale, significant negative correlations are diagnosed between the Near Strait transport and the Bering Slope and Alaskan Stream currents. Substantial correlations are also diagnosed between the eddy kinetic energy and Pacific Decadal Oscillation

Toward development of the 4Dvar data assimilation system in the Bering Sea: reconstruction of the mean dynamic ocean topography

The Bering Sea circulation is derived as a variational inverse of hydrographic profiles(temperature and salinity), atmospheric climatologies and historical observation of ocean currents. The important result of this study is estimate of the mean climatological sea surface height(SSH) that can be used as a reference for satellite altimetry sea level anomaly data in the Bering Sea region. Numerical experiments reveal that, when combined with satellite altimetry, the obtained reference SSH effectively constrains a realistic reconstruction of the Amukta Pass circulation

Variability of the Bering Sea circulation in the period 1992-2010

Sea surface height anomalies observed by satellites in 1992-2010 are combined with monthly climatologies of temperature and salinity to estimate circulation in the southern Bering Sea. The estimated surface and deep currents are consistent with independent velocity observations by surface drifters and Argo floats parked at 1,000 m. Analysis reveals 1-3-Sv interannual transport variations of the major currents with typical intra-annual variability of 3-7 Sv. On the seasonal scale, the Alaskan Stream transport is well correlated with the Kamchatka (0.81), Near Strait (0.53) and the Bering Slope (0.37) currents. Lagged correlations reveal a gradual increase of the time the lags between the transports of the Alaskan Stream, the Bering Slope Current and the Kamchatka Current, supporting the concept that the Bering Sea basin is ventilated by the waters carried by the Alaskan Stream south of the Aleutian Arc and by the flow through the Near Strait. Correlations of the Bering Sea currents with the Bering Strait transport are dominated by the seasonal cycle. On the interannual time scale, significant negative correlations are diagnosed between the Near Strait transport and the Bering Slope and Alaskan Stream currents. Substantial correlations are also diagnosed between the eddy kinetic energy and Pacific Decadal Oscillation