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Herkunft von Schelfwasser und Pazifischem Wasser in der arktischen Salzgehaltsschichtung abgeleitet von stabilen Sauerstoffisotopen

Ziel des Projektes ist eine Bestandsaufnahme der Wassermassenverteilung und der Zirkulation im Arktischen Ozean. Stabile Sauerstoffisotopen (delta18O) des Wassers ist ein konservativer Tracer und werden zusammen mit hydrochemischen Daten dazu verwendet das vom Schelf stammende Süßwasser (Flusswasser und Meereis-Schmelze oder Bildung) und die aus dem Pazifik stammende Komponente zu untersuchen. Auf diese Weise wird der Einfluss dieser Wassermassen in der arktischen Salzgehaltsschichtung (Halokline), dem Atlantischen Zwischenwasser und dem Tiefen- und Bodenwasser des Arktischen Ozeans quantifiziert werden. Es ist bekannt, dass die Verteilung der Pazifischen Komponente starken Veränderungen auf dekadischen Zeitskalen unterliegt aber auch in den Süßwasserverteilungen im Transpolaren Drift Strom wurden 2007 starke Variationen beobachtet welche somit auf zusätzliche jährliche Variationen hinweisen. Es ist nicht bekannt ob die 2007 beobachteten Variationen ein permanentes Phänomen sind und ob diese mit dem weitgehenden Fehlen des Pazifischen Wassers in diesem Zeitraum zusammenhängen. Die geplante flächendeckende und quantitative Erfassung der Süßwasserverteilung und des Pazifischen Wassers werden daher dazu beitragen, den Einfluss und die möglichen Rückkopplungsmechanismen der arktischen Hydrographie auf den arktischen und globalen Klimawandel weitergehend zu verstehen.

CASE Outcrop Data

The dataset comprises the locations of outcrops with respective information on the lithology, stratigraphy, rock age and tectonic data collected during the CASE expeditions. The data attributes include stereographic projections and sketches of tectonic structures derived from the outcrop data. At the end of the 1980s, BGR initiated the research program Circum-Arctic Structural Events (CASE) to reconstruct the plate tectonic processes during the evolution of the Arctic Ocean using terrestrial data from the surrounding continental margins. One of the scientific questions of the CASE programme is as simple as it is complex: How did the Arctic Ocean, this large basin between the Eurasian and North American continental plates, develop? There are still no conclusive answers to this question in terms of plate tectonics. In contrast to the marine expeditions of geophysicists in the Arctic Ocean, geologists on land along the various coastal areas of the Arctic Ocean can directly touch, examine and map rocks, structures, folds and fault zones and determine the respective ages of the movements. This makes it possible to directly compare rock units and deformation zones on different continental plates and thus also to reconstruct when these plates collided, how long they remained next to each other and when and how they separated again. Since the inception of BGR’s Arctic research, the primary focus and research areas have been along the continental margins between Spitsbergen and the Canadian Arctic Archipelago via Greenland, to the Yukon North Slope on the border with Alaska. On the opposite side of the Arctic Ocean, there have been expeditions to Yakutia, the mainland areas near the Laptev Sea, the New Siberian Islands and to the Polar Ural with Russian partners. An important method for the interpretation of the geological evolution of the Arctic is the examination of tectonic structures (faults, folds, cleavage etc.), the determination of the kinematics and the age of the tectonic movements.

Multibeam bathymetry processed data (dataset compilation) of RV POLARSTERN & RV MARIA S. MERIAN during 44 cruises from 1984 to 2024, Fram Strait, Greenland Sea, Arctic Ocean

The Long-Term Ecological Research observatory HAUSGARTEN was established by the Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung in the Fram Strait in summer 1999 to detect and track the impact of large-scale environmental changes on the marine ecosystem in the transition zone between the northern North Atlantic and the central Arctic Ocean. In this area, bathymetric data have been recorded with multibeam echosounders during 44 research expeditions on RV Polarstern and RV Maria S. Merian since 1984. From these data, a digital elevation model was generated and geostatistical analyses were performed to calculate geospatial derivatives and quantitative terrain descriptors for subsequent terrain analyses and habitat mapping. The dataset covers an area from 78°N to 81°N and 6°W to 12°E. To create the data product, archive data was used from seven different multibeam echosounders in various raw data formats. This data has been processed and cleaned with CARIS HIPS & SIPS, including sound velocity correction for datasets from 1999 and newer. Older datasets are calculated with a static sound velocity of 1500 m/s. Soundings where exported for gridding with Generic Mapping Tools (GMT) nearneighbor. The resulting Digital Elevation Model (DEM) is in the WGS84/Arctic Polar Stereographic (EPSG:3995) projection with a cell size of 100m x 100m. The hillshade was computed with a combination of slope and synthetic illumination with a vertical exaggeration of 10. Slope inclination was calculated with GDAL tool Slope with the formula of Zevenbergen and Thorne (1987) in degree. Terrain Ruggedness Index (TRI) was computed with the QGIS tool Ruggedness index following the approach of Riley et al. (1999) in meters. For the Bathymetric Position Indices (BPI), focal statistics have been calculated with the GRASS tool "r.neighbors" and the QGIS raster calculator following the concept of the Topographic Position Index (Weiss, 2001) with a circular reference area of 99 cells (broad) and 9 cells (fine). The additional coverage polygon layer gives and overview on the used datasets and their corresponding metadata. The map gives an overview on the LTER HAUSGARTEN area and the HAUSGARTEN 2024 DEM.

Clay and heavy minerals and total organic carbon in Arctic Ocean surface sediments – Data tables to distribution maps of Stein (2008)

Total organic carbon (TOC) and mineral assemblages are key data sets determined to characterize marine sediments in terms of sediment provenances, processes, and depositional environments. In a comprehensive review and synthesis (Stein, 2008), such data were compiled for Arctic Ocean surface sediments and shown in nine selected distribution maps: four maps of clay minerals (illite, smectite, chlorite, and kaolinite), four maps of heavy minerals (amphibole, clinopyroxene, epidote, and garnet), and one TOC map. The data used to produce these maps, are represented in the three tables of this data report. For details in background information and methodology see primary source literature cited here as well as the Stein (2008) synthesis.

Processed seismic data of Cruise Nares 2001

The Scientific staff and crew onboard CCGS Louis S. St. Laurent (LSL) returned September the 10th, 2001 from a scientific expedition to the Nares Strait, the northernmost waterway connecting the Arctic and Atlantic oceans. The data format is Society of Exploration Geophysicists SEG Y. The ice conditions in the strait required the support of Canada's largest ice breaker. The ship was a versatile platform for 34 scientists to accomplish their marine investigation. The LSL has a history of supporting international scientific expeditions including an oceanographic transect of the Arctic Ocean in 1994 and a biological study of the Canadian Arctic Islands in 1999. Germany (Bundesanstalt für Geowissenschaften und Rohstoffe, BGR) and Canada (Geological Survey of Canada) undertook a 5-week scientific cruise to study and explore the geological structure and evolution of the Nares Strait. The primary objective was the study of structural features relating to the formation of the Arctic Ocean and, in particular, the study of the Wegener Fault. This fault is a linear boundary between Greenland and Ellesmere Island which was noted by the German scientist Alfred Wegener in 1915 and later became the subject of a major scientific controversy. The co-operative cruise, which was planned over a period of 2 years, provided the basis for a wide range of scientific investigations, from marine seismic work and climate change studies through airborne magnetic investigations to geodetic survey measurements and geological sampling onshore. Systematic geophysical offshore studies in this key area had not been undertaken before. Where towing of seismic equipment was not possible because of ice coverage, magnetic maps were made using a helicopter-borne magnetic sensor system. Sediment and water samples taken during the cruise provide information on changes in climate and sea ice cover from the last ice-age to the present. An 11 m-long sediment core from outer Jones Sound is the longest core ever taken in the Canadian Arctic channels and holds clues to the detailed climate history of northern Baffin Bay.

Cell densities of the Arctic diatom Thalassiosira gravida in response to temperature, photoperiod and microbiome presence

In March 2023, cell densities of the Arctic diatom Thalassiosira gravida (isolated from the Central Arctic Ocean) were determined to calculate its growth rates at different temperatures and photoperiods in the presence and absence of its natural microbiome. Therefore, a full-factorial experimental design was chosen with two levels of temperature (9°C; 13.5°C) and photoperiod (16h; 24h), to which axenic and xenic diatom cultures were acclimated for one week in climate cabinets prior to the start of the actual growth experiment at a light intensity of 50 µmol photons m-2 s-1. With an initial cell density of 1500 cells/ml, axenic and xenic diatoms were grown under the respective experimental conditions until a cell density of approximately 15000 cells/ml was reached. Cell densities were determined microscopically using an inverted light microscope, following the procedure described in detail in Giesler et al. (2023, 10.3389/fmars.2023.1244639).

Nitrogen isotope and biomarker data during Late Paleocene–early Eocene

This dataset compiles raw measurements generated to investigate perturbations of the marine nitrogen cycle during the Paleocene–Eocene Thermal Maximum (PETM). It includes abundances of isoprenoidal GDGTs (isoGDGTs) and crenarchaeol mass accumulation rates, (ii) chromatographic peak areas of bacteriohopanetetrol (BHT) and BHT-x, and (iii) the nitrogen isotopic composition of bulk sediments (bulk sediment δ¹⁵N). Samples were collected from multiple ocean basins and regions: the Central Arctic Ocean (IODP 302–M0004), East Tasman Plateau in the Southwest Pacific (ODP Site 1172), Central Northern Caucasus (Kheu River), the New Jersey Shelf/Atlantic Coastal Plain (ODP 174AX Ancora), the Côte d'Ivoire–Ghana Transform Margin in the equatorial Atlantic (ODP 959), the Southeast Newfoundland Ridge in the central North Atlantic (IODP 1403), Fur Island, Denmark (Fur Formation), and the Tarim Basin, western China (Qimugen Formation). Lipid biomarker data were obtained using liquid chromatography coupled to mass spectrometry, and bulk nitrogen isotope data were measured by elemental analysis coupled to isotope-ratio mass spectrometry.

Helicopter-borne Magnetics NARES I + II (Kane Basin)

In May/June 2001, as part of the expedition NARES I, an aeromagnetic survey was carried out in the area of the eastern Kane Basin in cooperation with the Canadian GSC, in addition to the survey over the Robeson Channel and parallel to marine geophysical investigations with the Canadian icebreaker Louis S. St. Laurent. Another survey, NARES II, was conducted from Alexandra Fiord in 2003 and covered coastal areas of Ellesmere Island and the western Kane Basin. The aim of the research was to detect and localize the Wegener Fault, a transform fault between Ellesmere Island and NW Greenland, which is closely linked to the opening of the North Atlantic and the Arctic Ocean. The helicopter-borne magnetic surveys NARES I + II (Kane Basin) were carried out with a flight line spacing of 2 km, and control profiles were flown every 10 km. During the two expeditions, 11806 km of line data were collected (3573 km in 2001, and 8333 km in 2003), covering an area of approximately 20000 km². The aeromagnetic data were recorded by a magnetometer, which was towed approx. 25 m beneath the helicopter.

Helicopter-borne Magnetics NARES I (Robeson Channel)

During the German-Canadian Nares Strait Expedition in 2001, an aeromagnetic survey was carried out across the northern part of the Nares Strait including the Hall Basin, Judge Daly Promontory and in Robeson Channel in cooperation with the Canadian GSC. The aim of the research was to detect and localize the Wegener Fault, a transform fault between Ellesmere Island and NW Greenland, which is closely linked to the opening of the North Atlantic and the Arctic Ocean. The helicopter-borne magnetic survey NARES I (Robeson Channel) was carried out with a flight line spacing of 2 km, and control profiles were flown every 10 km. During the expedition, 5470 km of line data were collected. The aeromagnetic data were recorded by a magnetometer, which was towed approx. 25 m beneath the helicopter and recorded at a constant altitude of 305 m (1000 ft) above ground.

A validation data set of phytoplankton pigment concentrations and phytoplankton groups measured on water samples collected from various expeditions

This data set composes quality controlled in situ measurements of eight major pigments based on HPLC collected from various expeditions from 2016 to 2023. There are two subsets: subset 1 is the test dataset (99 matchups) extracted from and takes up 30 % of a global in situ PFT matchup data set, while the other 70 % was used for the retuning of the PFT algorithm for Sentinel 3 OLCI sensors. Subset 1 spans from 2016 to 2021 and is part of the global data set described in Xi et al. (2023): https://doi.pangaea.de/10.1594/PANGAEA.954738. Subset 2 containing 134 matchups is a newly compiled dataset that composites in situ PFT data collected from four recent mostly polar expeditions with the research vessel Polarstern (Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 2017), that are PS126 (May–June 2021), PS131/1 (June–Aug 2022) and PS136 (May–June 2023) in the north Atlantic to the Arctic Ocean, and PS133 (Oct–Nov 2022) in the Southern Ocean. The in situ PFT data were derived from quality-controlled HPLC pigment concentrations using diagnostic pigment analysis (DPA) with updated pigment-specific weighting coefficients following Xi et al. (2023). This published data set has been used to validate satellite PFT products generated for the EU funded Copernicus Marine Service (CMEMS, https://marine.copernicus.eu/), which are derived from multi-sensor ocean color reflectance data and sea surface temperature using an empirical orthogonal function based approach (Xi et al. 2020; 2021).

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