Nikolay P. Nezlin

Sea-surface signatures of the island mass effect phenomena around Madeira Island Northeast Atlantic

Abstract This is an introductory work that describes the manifestation of the island mass effect phenomena in the atmosphere and at the sea surface for a region of the ocean depleted from oceanographic work—the Madeira Archipelago (33°N, 17°W). The use of remote sensing tools becomes essential in recognizing some of the sea-surface features that characterize the island mass effect phenomena. AVHRR, coastal zone color scanner (CZCS), and SeaWiFS ancillary National Center for Environmental Prediction (NCEP) data, together with highly developed processing tools from PANORAMA (Processing and Automatic Navigation Of ReAl-time iMAges) allowed the detection of atmospheric Von Karman Vortex Streets, warm water surface wakes, leeward eddies, Azorean front, and localized upwelling. Results from the remote sensing analysis also helped to promote the reanalysis of historical in situ data for the manifestation of these island effects. IPIMAR cruises carried out between 1979 and 1982 collected temperature, salinity, density, and chlorophyll data, which were reinterpolated at the sea surface to study the island mass effect phenomena for the first time. Results have shown the formation of a warm water wake south of Madeira Island expanding 400 km offshore. The surface signature of the Azorean front, the so-called subtropical front, seems to take place within the Madeira latitude (33°N). North waters were consistently colder than the warm and salty southern waters. AVHRR data also revealed eddies and fronts being formed in the region. Leeward eddies were often observed in the flanks of the islands; CZCS data showed highly productive eddies in the west of Madeira Island. Localized cold water with high chlorophyll concentrations was also observed around the islands coast. A particularly dynamic area was the underwater ridge that connected Madeira and Desertas Islands. Future work should continue to sample these regions of interest with the simultaneous use of different satellite sensors. Vertical characterization of the different phenomena is needed.

Patterns of Seasonal and Interannual Changes of Surface Chlorophyll Concentration in the Black Sea Revealed from the Remote Sensed Data

Abstract Several years of CZCS-measured surface pigment’s concentrations in the Black Sea are analyzed to appraise the seasonal and year-to-year fluctuations of phytoplankton biomass and understand the causes of these fluctuations in terms of the Black Sea’s general dynamics. The pattern of seasonal variations is typical for subtropical rather than temperate regions. The range of the absolute value of plant pigment surface concentration measured by remote sensing does not differ greatly from the values measured by direct methods. The pattern of year-to-year variations seems to correlate with cyclic oscillations of winter air temperature. In western shallow regions it is also correlated with the Danube discharge intensity. More intensive winter–spring blooms and a slightly lower level of pigment concentration during warm season are typical for years of with a mild winter. The causes of these regularities seem to be the peculiarities of hydrological and meteorological regimes of the Black Sea. The intensity of winter–spring bloom of phytoplankton appears to depend on hydrological mechanism (i.e., the intensity of water mixing during winter period due to thermic convection and wind mixing) rather than the illumination intensity.

Mesoscale eddies and related processes in the northeastern Black Sea

Abstract Mesoscale dynamics in the northeastern Black Sea in Autumn 1993 and 1997 is considered on the basis of analysis of the NOAA AVHRR imagery together with relevant hydrographic measurements and meteorological information. Over the course from 6 September to 8 October 1997, five near-shore anticyclonic eddies (NAEs) about 40 km in diameter were observed within the region between Tuapse and the Kerch Strait, their movement speed reaching about 15 cm/s at separate parts of their trajectories. Separation of an NAE (NAE-1) from the coast in the region of a widening shelf/slope west of Novorossiysk and its transformation into deep-sea eddy was traced. Lifetime of the anticyclone was no less than 1 month, its mean offshore speed was about 4.3 cm/s. According to the SeaWiFS data, the increased chlorophyll a concentration (compared with the mean concentration at the center of the eastern part of the sea) was observed on 8 October 1997 in four “young” NAEs after an intense precipitation, the decreased one at the same time occurred in NAE-1, which was depleted of supply by shelf waters. In Summer 1993, a large NAE (about 95 km in diameter) was observed in the region between Tuapse and Gelendzhik. Evolution of the eddy from 3 June to 8 November 1993 was traced. Lifetime of the eddy exceeded 5 months. Its mean offshore speed to the southwest since its separation from the coast (around 17 August) in the Novorossiysk region was about 1.2 cm/s. The difference between dynamic situations in the same season (autumn) of 2 years, 1997 and 1993, was likely associated with peculiarities of atmospheric circulation and related intensity of cyclonic circulation in the Black Sea.

Primary production and plankton stocks in the Pacific Ocean and their seasonal variation according to remote sensing and field observations

Data collected from 20 years of observations by the P. P. Shirshov Institute of Oceanology (about 250 comprehensive ecosystem stations) are summarized to evaluate the primary production and biomass of the principal groups of plankton in the Pacific Ocean. The stations were classified into geographical regions according to satellite determined criteria. The areas of these regions were evaluated according to CZCS data from 1978 to 1986. The total value of primary production was evaluated as 26·9 Gt C year−1. Taking the “bottle effect” correction into account, this value may be as high as 45.6 Gt C year−1. Total biomass values of phytoplankton (134 Mt C), bacteria (86 Mt C), protozoa (26 Mt C) and mesoplankton (184 Mt C) were also calculated. Seasonal variabilities of all these values were remarkably insignificant.

Chapter 14 Remote-sensing studies of seasonal variations of surface chlorophyll-a concentration in the

Seasonal variations of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Coastal Zone Color Scanner (CZCS) measurements of surface chlorophyll-a concentration in the Black Sea are described. For areas where the water depth is greater than 200 m, surface chlorophyll-a concentration was maximum in winter. SeaWiFS surface chlorophyll-a concentrations in 1997-1998 were larger than CZCS data in 1978-1986; the change seems to result from both eutrophication and long-term climatic oscillations. In 1997-1998, the maximum surface chlorophyll-a concentration occurred during autumn instead of winter-spring; this seems to result from Danube River runoff, which is maximum in August 1997; the possible mechanism of this influence is discussed.