Description: Cold-water coral reefs occur at various sites along the European continental margin, like in the Mediterranean Sea, on carbonate mounds West off Ireland, or at shallower depths between 100 and 350 m on the Norwegian shelf. Their occurrence is related to different physical parameters like temperature, salinity, seawater density, dissolved oxygen, and to other environmental parameters such as internal wave activity, nutrient supply, strong currents, which keep sediment input low, etc. Here, we present first results from a long-term observation in one of the nortnermost cold-water coral reefs at 70.5°N - the Stjernsund in northern Norway. The Stjernsund is a 30 km long and up to 3.5 km wide sound connecting the open North Atlantic with a fjord system. A deep-seated SW-NE oriented morainic sill with varying depths (203-236 m) splits the more than 400 m deep sound into two troughs. Living Lophelia pertusa dominated reef complexes occur on the NW slope between 235 and 305 m water depths and on the SE slope between 245 and 280 m. To investigate the dominating physical and biogeochemical boundary conditions a new modular seafloor observatory, MoLab, consisting of five sea-floor observatories and two moorings was deployed for 100 days during the summer of 2012. The various lander systems and moorimgs were equipped with sensors to measure current velocities and directions, temperature, salinity, pressure, pH, turbidity, fluorescence, oxygen concentration and saturation. Results showed that near-bottom salinities, temperature and current velocities are dominated by a semi-diurnal tidal forcing (pronounced M2 constituent), which cause vertical water mass movements of up to 100 m. These influence large parts of the living reef. Closer examination revealed overturning cells on the south-eastern slope of the sill during high tide, when Atlantic Water flows over the sill. The appearance of living cold-water corals is limited to a density envelope of sigma-theta=27.25-27.50 kg/m-3, which marks the boundary between Norwegian Coastal Water and Atlantic Water. Globally, Lophelia pertusa lives in waters covering a wide range of physical and biogeochemical parameters. This new data sets indicates parameter ranges, of e.g. current velocities (15-30 cm/s), temperature (6.0-6.8°C) and salinity (34.1-34.8), pH (8.22-7.39), turbidity (0.1-0.9 NTU), and oxygen concentration (300-339 μM) that are in agreement with other cold-water coral reefs in the NE Atlantic. The overall circulation depicts a complex dynamic system with pronounced differences not only vertically, but also important horizontal changes on top of the sill.

Description: Cold-water corals are an object of world-wide research. Active exploration of the reef-building coral species has begun in the XX century with the development of the digital sea bottom mapping techniques and determines that cold-water corals can thrive in a wide range of depth below the photic zone from 43 m down to 3 380 m, but crucial ecological parameters governing the distribution are still not fully understood. In the focus of this study lies the northernmost living cold-water coral reef, known so far, which is located in the Stjernsund (70: 15′ N 22: 20′ E), Northern Norway. The main coral reef is formed by the scleractinia Lophelia pertusa. An underwater 4D Modular Laboratory, compiled of 5 landers and 2 moorings, was especially designed at the GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, to investigate the living coral communities of the Stjernsund. The elongated structure of the sound extends from SE to NW, connecting the North Atlantic with the Altafjord, is 30 km long and 3.5 km wide with the sill structure across it. From 1.06.2012 to 15.09.2012 the underwater laboratory was installed (434 and 438 POSEIDON cruises) on the sill recording oceanographically and biogeochemical data. Underwater observatory modules were installed on both slopes of the sill (one mooring and one lander on each slope) and on top of the sill (3 landers), so that the entire sill area was covered with measurements and water column, depending on the module settings, provides ADCP records. The Modular laboratory recorded the following physical and biochemical parameters: velocities and directions of the water flows, temperature, salinity, pH, turbidity, fluorescence, oxygen concentration and saturation. In this work data sets from 7 modules are analyzed in order to determine the ecological factors governing the uneven distribution of the living corals on the slopes of the sill and in order to reconstruct the water mass dynamics in the sound. The raw data was processed with the software Matlab. Results showed that near-bottom salinities, temperature and current velocities indicate a semi-diurnal tidal forcing (pronounced M2 constituent), which cause vertical water mass movements of up to 100 m, that influences large parts of the living reef. Reconstruction of the residual current flow in the sound has given an idea of the real water flow in the northern setting without tidal influence. Detailed examination of the water mass motions both diurnal and entire observation period has confirmed suggested theory The raw data was processed with the software Matlab. Results showed that near-bottom salinities, temperature and current velocities indicate a semi-diurnal tidal forcing (pronounced M2 constituent), which cause vertical water mass movements of up to 100 m, that influences large parts of the living reef. Reconstruction of the residual current flow in the sound has given an idea of the real water flow in the northern setting without tidal influence. Detailed examination of the water mass motions both diurnal and entire observation period has confirmed suggested theory stating that a turbulent cell occurs on the south-eastern slope of the sill at high tide conditions, when the Atlantic Water crosses over the sill. To investigate fluctuations of the ecological parameters and determine its influence on the corals, near-bottom water layers were analyzed with a daily resolution and over the entire observation period. Diurnal observations revealed that changes in temperature never exceeded 0.2 :C, salinity during the day changed not greater than 0.3 psu. Oxygen loggers revealed values in the range 10 μM and 4% for concentration and saturation respectively. Appearance of living cold-water corals lies within density envelope 27.25-27.50 kg m³, which marks the boundary between Norwegian Coastal Water and Atlantic Water. Lophelia pertusa as a globally distributed species can live in a wide range of physical and geochemical parameters. Observed data sets of the entire period present the agreeable with other explored living coral locations ranges of values of current velocities (15-30 cm/s), temperature (6.0-6.8:C) and salinity (34.1-34.8 ‰), pH (8.22-7.39), turbidity (0.1-0.9 NTU), fluorescence (0.04-0.16 mg/m³) and oxygen concentration (300-339 μM). Only the pH curve showed an unusual pattern unobserved at other locations. The pH value shows a linear decreasing trend during the summer period, reaching 7.4 pH. In this study several possible reasons for this drop are explored as the pH magnitude 7.6 is crucial for Lophelia reefs, this pH triggers dissolution process. Water flow in the Stjernsund, Northern Norway, depicts a complex dynamic system with pronounced differences not only vertically, but also important horizontal changes on top of the sill. Most likely that uneven distribution of living corals is influenced in greater value by parameters that have not been covered in this work. In this context the water dynamics, especially water motions over the sill, bringing Atlantic Water in the SE part of the sound, seem to play an essential role.

Description: Syngenetic permafrost deposits formed extensively on and around the arising Beringian subcontinent during the Late Pleistocene sea level lowstands. Syngenetic deposition implies that all material, both mineral and organic, freezes parallel to sedimentation and remains frozen until degradation of the permafrost. Permafrost is therefore a unique archive of Late Pleistocene palaeoclimate. Most studied permafrost outcrops are situated in the coastal lowlands of northeastern Siberia; inland sections are, however, scarcely available. Here, we describe the stratigraphical, cryolithological, and geochronological characteristics of a permafrost sequence near Batagay in the Siberian Yana Highlands, the interior of the Sakha Republic (Yakutia), Russia, with focus on the Late Pleistocene Yedoma ice complex (YIC). The recently formed Batagay mega-thaw slump exposes permafrost deposits to a depth of up to 80 m and gives insight into a climate record close to Verkhoyansk, which has the most severe continental climate in the Northern Hemi- sphere. Geochronological dating (optically stimulated luminescence, OSL, and 14C ages) and stratigraphic implications delivered a temporal frame from the Middle Pleistocene to the Holocene for our sedimentological interpretations and also revealed interruptions in the deposition. The sequence of lithological units indicates a succession of several distinct climate phases: a Middle Pleistocene ice complex indicates cold stage climate. Then, ice wedge growth stopped due to highly increased sedimentation rates and eventually a rise in temperature. Full interglacial climate conditions existed during accumulation of an organic-rich layer – plant macrofossils reflected open forest vegetation existing under dry conditions during Marine Isotope Stage (MIS) 5e. The Late Pleistocene YIC (MIS 4–MIS 2) suggests severe cold-stage climate conditions. No alas deposits, potentially indicating thermokarst processes, were detected at the site. A detailed comparison of the permafrost deposits exposed in the Batagay thaw slump with well-studied permafrost sequences,both coastal and inland, is made to highlight common features and differences in their formation processes and palaeo-climatic histories. Fluvial and lacustrine influence is tem-orarily common in the majority of permafrost exposures, but has to be excluded for the Batagay sequence. We interpret the characteristics of permafrost deposits at this location as a result of various climatically induced processes that are partly seasonally controlled. Nival deposition might have been dominant during winter time, whereas proluvial and aeolian deposition could have prevailed during the snowmelt period and the dry summer season.

Description: Ice wedges in the Yana Highlands of interior Yakutia – the most continental region of the Northern Hemisphere – were investigated to elucidate changes in winter climate and continentality that have taken place since the Middle Pleistocene. The Batagay megaslump exposes ice wedges and composite wedges that were sampled from three cryostratigraphic units: the lower ice complex of likely pre-Marine Isotope Stage (MIS) 6 age, the upper ice complex (Yedoma) and the upper sand unit (both MIS 3 to 2). A terrace of the nearby Adycha River provides a Late Holocene (MIS 1) ice wedge that serves as a modern reference for interpretation. The stable-isotope composition of ice wedges in the MIS 3 upper ice complex at Batagay is more depleted (mean δ18O about −35 ‰) than those from 17 other ice-wedge study sites across coastal and central Yakutia. This observation points to lower winter temperatures and therefore higher continentality in the Yana Highlands during MIS 3. Likewise, more depleted isotope values are found in Holocene wedge ice (mean δ18O about −29 ‰) compared to other sites in Yakutia. Ice-wedge isotopic signatures of the lower ice complex (mean δ18O about −33 ‰) and of the MIS 3–2 upper sand unit (mean δ18O from about −33 ‰ to −30 ‰) are less distinctive regionally. The latter unit preserves traces of fast formation in rapidly accumulating sand sheets and of post-depositional isotopic fractionation.

Description: Syngenetic permafrost deposits formed extensively on and around the arising Beringian subcontinent during the Late Pleistocene sea level lowstands. Syngenetic deposition implies that all material, both mineral and organic, freezes parallel to sedimentation and remains frozen until degradation of the permafrost. Permafrost is therefore a unique archive of Late Pleistocene palaeoclimate. Most studied permafrost outcrops are situated in the coastal lowlands of northeastern Siberia; inland sections are, however, scarcely available. Here, we describe the stratigraphical, cryolithological, and geochronological characteristics of a permafrost sequence near Batagay in the Siberian Yana Highlands, the interior of the Sakha Republic (Yakutia), Russia, with focus on the Late Pleistocene Yedoma ice complex (YIC). The recently formed Batagay mega-thaw slump exposes permafrost deposits to a depth of up to 80 m and gives insight into a climate record close to Verkhoyansk, which has the most severe continental climate in the Northern Hemisphere. Geochronological dating (optically stimulated luminescence, OSL, and 14C ages) and stratigraphic implications delivered a temporal frame from the Middle Pleistocene to the Holocene for our sedimentological interpretations and also revealed interruptions in the deposition. The sequence of lithological units indicates a succession of several distinct climate phases: a Middle Pleistocene ice complex indicates cold stage climate. Then, ice wedge growth stopped due to highly increased sedimentation rates and eventually a rise in temperature. Full interglacial climate conditions existed during accumulation of an organic-rich layer - plant macrofossils reflected open forest vegetation existing under dry conditions during Marine Isotope Stage (MIS) 5e. The Late Pleistocene YIC (MIS 4-MIS 2) suggests severe cold-stage climate conditions. No alas deposits, potentially indicating thermokarst processes, were detected at the site. A detailed comparison of the permafrost deposits exposed in the Batagay thaw slump with well-studied permafrost sequences, both coastal and inland, is made to highlight common features and differences in their formation processes and palaeoclimatic histories. Fluvial and lacustrine influence is temporarily common in the majority of permafrost exposures, but has to be excluded for the Batagay sequence. We interpret the characteristics of permafrost deposits at this location as a result of various climatically induced processes that are partly seasonally controlled. Nival deposition might have been dominant during winter time, whereas proluvial and aeolian deposition could have prevailed during the snowmelt period and the dry summer season.