Sedimentology and geochemistry of core GIK23258-2 in the Barents Sea

At the western continental margin of the Barents Sea, 75°N, hemipelagic sediments provide a record of Holocene climate change with a time resolution of 10-70 years. Planktic foraminifera counts reveal a very early Holocene thermal optimum 10.7-7.7 kyr BP, with summer sea surface temperatures (SST) of 8°C and a much enhanced West Spitsbergen Current. There was a short cooling between 8.8 and 8.2 kyr BP. In the middle and late Holocene summer, SST dropped to 2.5°-5.0°C, indicative of reduced Atlantic heat advection, except for two short warmings near 2.2 and 1.6 kyr BP. Distinct quasi-periodic spikes of coarse sediment fraction (with large portions of lithic grains, benthic and planktic foraminifera) record cascades of cold, dense winter water down the continental slope as a result of enhanced seasonal sea ice formation and storminess on the Barents shelf over the entire Holocene. The spikes primarily cluster near recurrence intervals of 400-650 and 1000-1350 years, when traced over the entire Holocene, but follow significant 885-/840- and 505-/605-year periodicities in the early Holocene. These non-stationary periodicities mimic the Greenland-[Formula: See Text]Be variability, which is a tracer of solar forcing. Further significant Holocene periodicities of 230, (145) and 93 years come close to the deVries and Gleissberg solar cycles.

(Table 1) Statistics of size measurements of Lagenoeca antarctica sp. n. and Salpingoeca abyssalis sp. n. (floating form) sampled during POLARSTERN cruise ANT-XXII/2 and METEOR cruise M63/2

Despite their high abundance and their high importance for the oceanic matter flux, heterotrophic nanoflagellates are only poorly studied in the deep-sea regions. Studies on the choanoflagellate distribution during two deep-sea expeditions, to the South Atlantic (5038 m) and Antarctica (Weddell Sea, 2551 m), revealed the deepest records of choanoflagellates so far. A new species, (Lagenoeca antarctica) with a conspicuous spike structure on the theca is described from deep Antarctic waters. Lagenoeca antarctica sp. n. is a solitary unstalked free living salpingoecid-like choanoflagellate. The protoplast is surrounded by a typical theca with unique spikes only visible in SEM micrographs. The ovoid cell nearly fills the whole theca and ranges in size from 4 to 6 µm. The collar measures 2-3 µm and the flagellum 3-5 µm. A second species, Salpingoeca abyssalis sp. n., was isolated from the abyssal plain of the South Atlantic (5038 m depth). Floating and attached forms were observed. The protoplast ranges from to 2 to 4 µm in length and 1 to 2 µm in width. The collar is about the same length as the protoplast and the flagellum has 2 to 2.5 × the length of the protoplast. Phylogenetic analyses based on a fragment of SSU rDNA revealed Salpingoeca abyssalis to cluster together with a marine isolate of Salpingoeca infusionum while Lagenoeca antarctica clusters separately from the other codonosigid and salpingoecid taxa. Salpingoeca abyssalis and an undetermined Monosiga species seems to be the first choanoflagellate species recorded from the abyssal plain.

Long-term eddy-covariance measurements from FINO2 platform above the Baltic Sea

The estimation of the carbon dioxide (CO2) fluxes above the open ocean plays an important role for the determination of the global carbon cycle. A frequently used method therefore is the eddy-covariance technique, which is based on the theory of the Prandl-layer with height-constant fluxes in the atmospheric boundary layer. To test the assumption of the constant flux layer, in 2008 measurements of turbulent heat and CO2 fluxes were started within the project Surface Ocean Processes in the Anthropocene (SOPRAN) at the research platform FINO2. The FINO2 platform is situated in the South-west of the Baltic Sea, in the tri-border region between Germany, Denmark, and Sweden. In the frame of the Research project SOPRAN, the platform was equipped with additional sensors in June 2008. A combination of 3-component sonic anemometers (USA-1) and open-path infrared gas analyzers for absolute humidity (H2O) and CO2 (LICOR 7500) were installed at a 9m long boom directed southward of the platform in two heights, at 6.8 and 13.8m above sea surface. Additionally slow temperature and humidity sensors were installed at each height. The gas analyzer systems were calibrated before the installation and worked permanently without any calibration during the first measurement period of one and a half years. The comparison with the measurements of the slow sensors showed for both instruments no significant long-term drift in H2O and CO2. Drifts on smaller time scales (in the order of days) due to the contamination with sea salt, were cleaned naturally by rain. The drift of both quantities had no influence on the fluctuation, which, in contrast to the mean values, are important for the flux estimation. All data were filtered due to spikes, rain, and the influence of the mast. The data set includes the measurements of all sensors as average over 30 minutes each for one and a half years, June 2008 to December 2009, and 10 month from November 2011 to August 2012. Additionally derived quantities for 30 minutes intervals each, like the variances for the fast-sensor variables, as well as the momentum, sensible and latent heat, and CO2 flux are presented.

Sea-surface temperature reconstruction in the Southwest Pacific

Uniquely in the Southern Hemisphere the New Zealand micro-continent spans the interface between a subtropical gyre and the Subantarctic Circumpolar Current. Its 20° latitudinal extent includes a complex of submerged plateaux, ridges, saddles and basins which, in the present interglacial, are partial barriers to circulation and steer the Subtropical (STF) and Subantarctic (SAF) fronts. This configuration offers a singular opportunity to assess the influence of bottom topography on oceanic circulation through Pleistocene glacial - interglacial (G/I) cycles, its effect on the location and strength of the fronts, and its ability to generate significant differences in mixed layer thermal history over short distances. For this study we use new planktic foraminiferal based sea-surface temperature (SST) estimates spanning the past 1 million years from a latitudinal transect of four deep ocean drilling sites. We conclude that: 1. the effect of the New Zealand landmass was to deflect the water masses south around the bathymetric impediments; 2. the effect of a shallow submerged ridge on the down-current side (Chatham Rise), was to dynamically trap the STF along its crest, in stark contrast to the usual glacial-interglacial (G-I) meridional migration that occurs in the open ocean; 3. the effect of more deeply submerged, downstream plateaux (Campbell, Bounty) was to dynamically trap the SAF along its steep southeastern margin; 4. the effects of saddles across the submarine plateaux was to facilitate the development of jets of subtropical and subantarctic surface water through the fronts, forming localized downstream gyres or eddies during different phases in the G-I climate cycles; 5. the deep Pukaki Saddle across the Campbell-Bounty Plateaux guided a branch of the SAF to flow northwards during each glacial, to form a strong gyre of circumpolar surface water in the Bounty Trough, especially during the mid-Pleistocene Climate Transition (MIS 22-16) when exceptionally high SST gradients existed across the STF; 6. the shallower Mernoo Saddle, at the western end of the Chatham Rise, provided a conduit for subtropical water to jet southwards across the STF in the warmest interglacial peaks (MIS 11, 5.5) and for subantarctic water to flow northwards during glacials; 7. although subtropical or subantarctic drivers can prevail at a particular phase of a G-I cycles, it appears that the Antarctic Circumpolar Current is the main influence on the regional hydrography. Thus complex submarine topography can affect distinct differences in the climate records over short distances with implications for using such records in interpreting global or regional trends. Conversely, the local topography can amplify the paleoclimate record in different ways in different places, thus enhancing its value for the study of more minor paleoceanographic influences that elsewhere are more difficult to detect. Such sites include DSDP 594, which like some other Southern Ocean sites, has the typical late Pleistocene asymmetrical saw-tooth G-I climate pattern transformed to a gap-tooth pattern of quasi-symmetrical interglacial spikes that interrupt extended periods of minimum glacial temperatures.