Beschreibung: Between Greenland and Spitsbergen, Fram Strait is a region where cold ice-covered Polar Water exits the Arctic Ocean with the East Greenland Current (EGC) and warm Atlantic Water enters the Arctic Ocean with the West Spitsbergen Current (WSC). In this compilation, we present two different data sets from plankton ecological observations in Fram Strait: (1) long-term measurements of satellite-derived (1998-2012) and in situ chlorophyll a (chl a) measurements (mainly summer cruises, 1991-2012) plus protist compositions (a station in WSC, eight summer cruises, 1998-2011); and (2) short-term measurements of a multidisciplinary approach that includes traditional plankton investigations, remote sensing, zooplankton, microbiological and molecular studies, and biogeochemical analyses carried out during two expeditions in June/July in the years 2010 and 2011. Both summer satellite-derived and in situ chl a concentrations showed slight trends towards higher values in the WSC since 1998 and 1991, respectively. In contrast, no trends were visible in the EGC. The protist composition in the WSC showed differences for the summer months: a dominance of diatoms was replaced by a dominance of Phaeocystis pouchetii and other small pico- and nanoplankton species. The observed differences in eastern Fram Strait were partially due to a warm anomaly in the WSC. Although changes associated with warmer water temperatures were observed, further long-term investigations are needed to distinguish between natural variability and climate change in Fram Strait. Results of two summer studies in 2010 and 2011 revealed the variability in plankton ecology in Fram Strait.

Beschreibung: At each study station, surface water temperature (±0.2°C) and salinity (±0.06) were measured in situ by triplicate readings with a multiparameter probe (Horiba U-10, Japan). Using Niskin bottles, surface water samples were collected for quantification of plankton and estimations of chlorophyll a. For the former, 250 ml were fixed with Lugol's solution (1% final concentration) and kept in the dark until analysis under the microscope, while for chlorophyll a, a volume of 200–250 mL was filtrated onboard through filter GF/C and kept at -20°C.

Beschreibung: Raw data acquired by two thermosalinographs (SBE21, SeaBird GmbH) on board RV Polarstern were processed to yield a calibrated and validated data set of temperature, conductivity and salinity during expedition PS121. Both sensors were equipped with a more accurate external temperature sensor (SBE38, Sea-Bird GmbH). Data were downloaded from the DAVIS SHIP data base (https://dship.awi.de) with a resolution of 1 sec. The raw hex data were converted to temperature and conductivity while a sensor drift correction was applied using calibration coefficients from before and after the expedition. Salinity was calculated according to the instructions from the Practical Salinity Scale PSS-78, using the obtained (internal) temperature and conductivity data and a pressure of 11 dbar which represents the water depth of the inlet of the TSG system on Polarstern. A speed filter of 0.5 knots minimum speed was applied. Processed data are provided as 10min means of seawater salinity, conductivity and temperature, aligned with position data taken from the master track of PS121 (doi:10.1594/PANGAEA.908157). Further details and evaluation of the data is outlined in the data processing report found at the EPIC repository under URL (https://hdl.handle.net/10013/epic.7fffb528-06bd-48ae-8489-cea0444c4eab).

Beschreibung: Time series data of physical oceanography (seawater conductivity, temperature, pressure, salinity), ocean current velocities and hydroacoustics were obtained from mooring F4-18 in the Fram Strait in July 2018 - August 2019 as part of the Helmholtz infrastructure program Frontiers in Arctic Marine Monitoring (FRAM) and the long-term monitoring program at AWI HAUSGARTEN. The mooring was deployed during Polarstern expedition PS114, and recovered during PS121. The attached archive contains raw data files of 6 Seabird SBE37 microcats (nominal depths: 63m, 150m, 250m, 500m, 731m, 1202m; sampling interval 1h), one RDI Workhorse Longranger ADCP (depth: 380m; sampling interval: 1h) and two AADI RCM11 current meters (depths: 730m, 1208m; sampling interval: 2h). The mooring also included a Develogic Sonovault (nominal depth: 800m; data archived elsewhere). Auxiliary information such as sensor calibration sheets, mooring diagrams and schedule files are also provided, if applicable.