Composition and fluxes of sinking particulate material and bottom sediments in the northeast Black Sea in 1998-1999

For the first time deep-sea mooring stations with sediment traps were deployed in the northeast Black Sea. One sediment trap for long-term studies was located at Station 1 (44°15'N, 37°43'E, deployment depth 1800 m, depth 1900 m). The trap collected sinking sedimentary material from January to May 1998. Material collectors were changed every 15 days. Other stations with sediment traps for short-term studies (September-October 1999) were located on the shelf: Station 2 (44°16'N, 38°37'E, deployment depth 45 m, depth 50 m) and on the bottom of the canyon: Station 3 (44°16'N, 38°22'E, deployment depth 1145 m, depth 1150 m), Station 4 (44°11'N, 38°21'E, deployment depths 200, 1550, 1650 m, depth 1670 m). Collected material indicates that vertical particle fluxes are controlled by seasonal changes of in situ production and by dynamics of terrigenous matter input. Higher vertical particle flux of carbonate and biogenic silica was in spring due to bloom of plankton organisms. Maximum of coccolith bloom is in April-May. Bloom of diatoms begins in March. In winter and autumn lithogenic material dominates in total flux. Its amount strongly depends on storms and river run-off. Suspended particle material differs from surface shelf sediments by finer particles (mainly clay fraction) and high content of clay minerals and biogenic silica. This material may form lateral fluxes with higher concentration of particles transported along the bottom of deep-sea canyons from the shelf to the deep basin within the nepheloid layer. In winter such transportation of sedimentary material is more intensive due to active vertical circulation of water masses.

Tab. 1: Winter temperatures at the west coast of Greenland

Ist die Tatsache ungewöhnlicher Temperaturzunahme im Nordpolarraum in den letzten Jahrzehnten durch zahlreiche Publikationen allgemein bekannt, so möchte ich hier auf einige sehr bemerkenswerte, in jüngster Zeit von mir aufgedeckte Erscheinungen und Beziehungen hinweisen. 1. Die Milderung der Wintertemperatur an der W-Küste Grönlands. Bildet man die Wintertemperaturdifferenzen: Godthab minus Jakobshavn, so zeigt sich für die untersuchte Reihe 1876-1939: 2. eine periodische Schwankung mit sehr gut ausgeprägten Maximis um die Mitte der Neunzigerjahre und um 1920, Minima um 1880, 1905 und Ende der 20er Jahre, das besonders abgeschwächt ist; seitdem ist diese Differenz wieder in Zunahme begriffen; es zeigt sich somit auch hier meine an zahlreichen Gebieten von der Äquatorial bis zur Polarzone aufgedeckte 24 jährige Witterungsperiode. 3. Die Abschwächung der Winter-Temperaturdifferenz von Godthaah bis Jakobshavn ist (trotz der relativ nur geringen Entfernung von kaum 600 km) als ungewöhnlich hoch zu betrachten. Um diese Verhältnisse eindrucksvoll darlegen zu können, ist die klare Darlegung durch Tabellen unerläßlich.

Biomass of picophytoplankton in the Black Sea in winter 1991

Studies of picophytoplankton were carried out in the open Black Sea from February to April 1991 with concomitant blooming of diatoms. During this period cyanobacteria predominated in picoplankton averaging 98.8% of total picophytoplankton abundance and 95% of total picoplankton biomass. In February number of cells reached 1.5x10**9 per liter in the East Black Sea. Picoplankton biomass decreased during the observation period. From February to March biomass varied from 452 to 4918 mg/m**2 (av. 1632 mg/m**2), and from March through April from 4 to 656 mg/m**2 (av. 190 mg/m**2). Vertical distribution of picoplankton was determined by the upper margin of the main pycnocline. The major part of picoplankton biomass occurred in the mixed layer. With appearance of seasonal pycnoclines in the last days of March maximum biomass occurred under the upper mixed layer. No relationship was observed between Nitzschia delicatula bloom and picoplankton.

Isotopic composition of modern ice wedges and winter precipitation in the Laptev Sea region (Table 2)

The first step for the application of stable isotope analyses of ice wedges for the correct paleoclimatic reconstruction supposes the study of the isotopic composition of modern ice wedges and their relationship with the isotopic composition of modern precipitation. The purpose of this research is to present, to analyze and to discuss new data on isotopic composition (d18O, dD, 3H) of modern ice wedges obtained in the Laptev Sea region in 1998-99. Investigations were carried out at two sites: on Bykovsky Peninsula in 1998 and on Bol'shoy Lyakhovsky Island in 1999 and were based on the combined application of both tritium CH) and stable isotope (d18O, dD) analyses. Tritium analyses of the atmospheric precipitation collected during two field seasons show seasonal variations: high tritium concentration in snow (to a maximum of 207 TU) and low values of tritium concentration (<20 TU) in rain. High tritium concentrations are also observed in the surface water, in suprapermafrost ground waters, and in the upper part of permafrost. High tritium concentrations range between 30-40 TU and 750 TU in the studied modern ice wedges (active ice wedges), which let us believe that they are of modern growth. Such high tritium concentrations in ice wedges can not be associated with old thermonuclear tritium because of the radioactive decay. High tritium concentrations found in the snow cover in 1998/99, in the active layer and in the upper part of permafrost give evidence of modern (probably the last decade) technogenic tritium arrival from the atmosphere on to the Earth surface in the region. The comparison of the isotopic composition (d18O, dD and d-excess) of active ice wedges and modern winter precipitation in both sites shows: 1) the isotopic composition of snow correlates linearly with a slope close to 8.0 and parallel to the GMWL at both sites; 2) the mean isotopic composition of active ice wedges on Bykovsky Peninsula is in good agreement with the mean isotopic composition of modern snow; 3) the isotopic composition of active ice wedges and snow on Bol'shoy Lyakhovsky Island are considerably different. There are low values of d-excess in all studied active ice wedges (mean value is about 4.8 per mil), while in snow, the mean value of d-excess is about 9.5 per mil. Possible reasons for this gap are the following: 1) the modification of the isotopic composition in snow during the spring period; 2) changes in the isotopic composition of ice wedges due to the process of ice sublimation in open frost cracks during the cold period; 3) mixing of snowmelt water with different types of surface water during the spring period; 4) different moisture source regions.