ALBERT

Description: Radium isotopes are produced by decay of an isotope of thorium, a highly particle reactive element. Radium is relatively soluble in seawater such that once a thorium isotope in suspended or bottom sediments decays, a fraction of the produced radium isotope may be released to solution. 224Ra (3.7-day half-life) and 223Ra (11.4-day half-life) are used extensively as tracers for interaction on the shelf and for submarine groundwater discharge (SGD). 228Ra is strongly enriched in shelf waters and in the Transpolar Drift (TPD) and its half-life (5.8 years) is well suited to study the fate of this shelf-derived water in the central Arctic. This dataset collected in the framework of GEOTRACES during PS94 in 2015 shows that the input of 228Ra in the TPD has increased since previous studies in 2007 and 2011. The distribution of 228Ra-daughter 228Th (1.9 y half-life) and the 228Th/228Ra ratio are measured to trace particle fluxes. The accumulation of 226Ra (1620 y half-life) in the deep Makarov Basin can be used as a measure of basin ventilation time.

Description: Radium isotopes are produced by decay of an isotope of thorium, a highly particle reactive element. Radium is relatively soluble in seawater such that once a thorium isotope in suspended or bottom sediments decays, a fraction of the produced radium isotope may be released to solution. 224Ra (3.7-day half-life) and 223Ra (11.4-day half-life) are used extensively as tracers for interaction on the shelf and for submarine groundwater discharge (SGD). 228Ra is strongly enriched in shelf waters and in the Transpolar Drift (TPD) and its half-life (5.8 years) is well suited to study the fate of this shelf-derived water in the central Arctic. This dataset collected in the framework of GEOTRACES during PS94 in 2015 shows that the input of 228Ra in the TPD has increased since previous studies in 2007 and 2011. The distribution of 228Ra-daughter 228Th (1.9 y half-life) and the 228Th/228Ra ratio are measured to trace particle fluxes. The accumulation of 226Ra (1620 y half-life) in the deep Makarov Basin can be used as a measure of basin ventilation time.

Description: Measurements of stable water isotopes (δ Deuterium, δ18O, δ13C) from the water column in the Fram Strait from the POLARSTERN cruises PS92 (ARK-XXIX/1, TRANSSIZ) and PS93.1 (ARK-XXIX/2.1) in May to July 2015. δ Deuterium and δ18O were measured with a Picarro 2130i CRDS System, δ13C with a Finnigan MAT 252 gas isotope ratio mass spectrometer with Gasbench 2 at MARUM - Center for Marine Environmental Sciences. The measurements were conducted in 2020/2021.

Description: During the winter expedition (Ti12) a standalone CTD (Seabird 19+) was lowered through an ice hole along with Nansen water samplers. Stable oxygen isotopes were analysed at the Stable Isotope Laboratory of COAS at Oregon State University (Corvallis, USA) applying the CO2-water isotope equilibration technique and analysed by dual inlet mass spectrometry (Thermo, DeltaPlus XL). The overall measurement precision for all δ18O analysis was ±0.04‰. The 18O/16O ratios were calibrated with Vienna Standard Mean Ocean Water (VSMOW) and reported in the usual δ-notation (Craig, 1961). For a quantitative interpretation of the oxygen isotope data, an exact match of salinity and δ18O values is essential. Therefore, in addition to CTD measurements, bottle salinity was determined directly within the water samples taken for δ18O analysis using an AutoSal 8400A salinometer (Fa. Guildline) with a precision of ±0.003 and an accuracy greater than ±0.005.

Description: Oxygen and hydrogen isotopic ratio samples were collected from sea ice and water samples. Coring and sampling were completed at six locations on July 25 for measurement of salinity and stable oxygen isotopic composition to better understand the meltwater sources for under-ice meltwater and false bottoms. Cores were collected using a corer (9 cm inner diameter; Mark II coring system, Kovacs Enterprises, US), and ice samples were collected from the bottom 10 centimeters of the ice core in 5 cm increments (0-5 and 5-10 cm above the bottom) and from the false bottom ice. Under-ice meltwater layer samples and water from directly below the false bottom were collected using a peristaltic pump. In order to minimize contamination from coring activities, under-ice meltwater samples from the meltwater layer in the void space between ice and false bottom were collected prior to coring through the false bottom. Surface melt pond water samples were collected by dipping plastic sample cups (rinsed with milliQ water) in the melt ponds where cores were collected, prior to ice coring. In total, ice samples were collected from six cores –– five of which included false bottoms –– and water samples were collected from four surface melt ponds, three under-ice melt water layers, and seawater beneath false bottoms at four locations. Locations are shown on map (Figure 2) as pink dashes. Ice samples were melted onboard the R/V Polarstern, and salinities of all water and ice samples were measured onboard using a calibrated YSI model 30 probe (salinity is given in PSS-78 scale, unitless). Vials for oxygen isotope composition were shipped to the AlfredWegener Institute (AWI) ISOLAB Facility in Potsdam, Germany, where they were analyzed for stable water isotopes with Finnigan MAT Delta-S mass spectrometers using equilibration techniques. The oxygen isotope composition is given as per mil difference relative to VSMOW (‰, Vienna Standard Mean Ocean Water), with an internal 1 sigma error better than 0.1‰ for delta 18O (Meyer et al., 2000). See attached diagram for a visualization of where the samples were collected.

Description: We present sea ice temperature and salinity data from first-year ice (FYI) and second-year ice (SYI) relevant to the temporal development of sea ice permeability and brine drainage efficiency from the early growth phase in October 2019 to the onset of spring warming in May 2020. Our dataset was collected in the central Arctic Ocean during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 to 2020. MOSAiC was an international transpolar drift expedition in which the German icebreaker RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. In October 2019, RV Polarstern moored to an ice floe in the Siberian sector of the Arctic at 85 degrees north and 137 degrees east to begin the drift towards the North Pole and the Fram Strait via the Transpolar Drift Stream. The data presented here were collected during the first three legs of the expedition, so all the coring activities took place on the same floe. The end dates of legs 1, 2, and 3 were 13 December, 24 February, and 4 June, respectively. The dataset contributed to a baseline study entitled, Deciphering the properties of different Arctic ice types during the growth phase of the MOSAiC floes: Implications for future studies. The study highlights downward directed gas pathways in FYI and SYI by inferring sea ice permeability and potential brine release from several time series of temperature and salinity measurements. The physical properties presented in this paper lay the foundation for subsequent analyses on actual gas contents measured in the ice cores, as well as air-ice and ice-ocean gas fluxes. Sea ice cores were collected with a Kovacs Mark II 9 cm diameter corer. To measure ice temperatures, about 4.5 cm deep holes were drilled into the core (intervals varied by site and leg) . The temperatures were measured by a digital thermometer within minutes after the cores were retrieved. The ice cores were placed into pre-labelled plastic sleeves sealed at the bottom end. The ice cores were transported to RV Polarstern and stored in a -20 degrees Celsius freezer. Each of the cores was sub-sampled, melted at room temperature, and processed for salinity within one or two days. The practical salinity was estimated by measuring the electrical conductivity and temperature of the melted samples using a WTW Cond 3151 salinometer equipped with a Tetra-Con 325 four-electrode conductivity cell. The practical salinity represents the the salinity estimated from the electrical conductivity of the solution. The dataset also contains derived variables, including sea ice density, brine volume fraction, and the Rayleigh number.

Description: Sea ice cores were collected from the Biogeochemistry (BGC) team at different stations located on the main ice floe of MOSAiC expedition. Flat sea ice on the floe was categorized into three types based on the age: sea ice which grew during the same winter referred to as First-Year-Ice (FYI); sea ice which had survived one or more summer melting periods referred to as Second-Year-Ice (SYI). Sea ice cores were collected using a Kovacs Mark II 9 cm diameter corer. The core was extracted and placed in an aluminum holder equipped with a metric ruler. Using a standard Kovacs ice thickness gauge, the freeboard was taken and the length of the core was measured. The snow on top of the sea ice was brushed off the top of the cores to minimize the snow affecting the ice surface. Onboard RV Polarstern, the cores were cut in 10 cm sections using a handsaw at 4° C (leg 1) or an electric saw at -20° C (legs 2 and 3). Each section was transferred into a gas-tight TedlarTM bag. The closed bags were carefully degassed with a vacuum pump (NKF Neuberger, type N035). Melting occurred within 12 to 15 hours in a water bath in the dark. After shaking the melted ice within the TedlarTM bags, discrete sampling started by first rising the melt water carefully through a Tygon tube connected with the opened valves of the gas tide bags and then into prepared sample vials. Here we present the data from samples collected at Main Core Site (MCS) at the Dark Sector (DS). Oxygen and hydrogen isotope analyses were carried out at the ISOLAB Facility at AWI Potsdam (https://hdl.handle.net/10013/sensor.ddc92f54-4c63-492d-81c7-696260694001) with mass spectrometers (DELTA-S Finnigan MAT, USA): https://hdl.handle.net/10013/sensor.af148dea-fe65-4c87-9744-50dc4c81f7c9 https://hdl.handle.net/10013/sensor.62e86761-9fae-4f12-9c10-9b245028ea4c employing the equilibration method (details in Meyer et al., 2000). δ18O and δD values were given in per mil (‰) vs. Vienna standard mean ocean water (V-SMOW) as the standard. The second order parameter d excess was computed according to: d excess = δD-8 δ18O (Dansgaard, 1964).

Description: Here we present a merged and calibrated dataset of temperature, practical salinity and dissolved organic matter (DOM) fluorescence obtained from several Ice Tethered Profilers (ITPs) deployed across the central Arctic (2011-2016). The data offer a unique spatial coverage of the distribution of DOM in the surface 800 m below Arctic sea ice. A total of 5044 profiles are gathered. The ITP data are level 3 data products pressure-bin-averaged at 1-db vertical resolution with depth down to either 200 or approximately 750 m. Data (max 800m depth) from CTD casts made during two oceanographic cruises are also included. These were used as part of the calibration and validation of the ITP calibration routines. The cruises were PS94 (ARK-XXIX/3) with POLARSTERN in 2015 and NAACOS with DANA in 2012. The presented DOM fluorescence data are smoothed, corrected for instrument drift and calibrated to provide intercomparable data across the sensors. Fluorescence is reported in Raman Units (nm-1), and comparable to laboratory measurements conducted according to current community recommendations.

Description: Here we present a merged and calibrated dataset of temperature, practical salinity and dissolved organic matter (DOM) fluorescence obtained from several Ice Tethered Profilers (ITPs) deployed across the central Arctic (2011-2016). The data offer a unique spatial coverage of the distribution of DOM in the surface 800 m below Arctic sea ice. A total of 5044 profiles are gathered. The ITP data are level 3 data products pressure-bin-averaged at 1-db vertical resolution with depth down to either 200 or approximately 750 m. Data (max 800m depth) from CTD casts made during two oceanographic cruises are also included. These were used as part of the calibration and validation of the ITP calibration routines. The cruises were PS94 (ARK-XXIX/3) with POLARSTERN in 2015 and NAACOS with DANA in 2012. The presented DOM fluorescence data are smoothed, corrected for instrument drift and calibrated to provide intercomparable data across the sensors. Fluorescence is reported in Raman Units (nm-1), and comparable to laboratory measurements conducted according to current community recommendations.

Description: Here we present a merged and calibrated dataset of temperature, practical salinity and dissolved organic matter (DOM) fluorescence obtained from several Ice Tethered Profilers (ITPs) deployed across the central Arctic (2011-2016). The data offer a unique spatial coverage of the distribution of DOM in the surface 800 m below Arctic sea ice. A total of 5044 profiles are gathered. The ITP data are level 3 data products pressure-bin-averaged at 1-db vertical resolution with depth down to either 200 or approximately 750 m. Data (max 800m depth) from CTD casts made during two oceanographic cruises are also included. These were used as part of the calibration and validation of the ITP calibration routines. The cruises were PS94 (ARK-XXIX/3) with POLARSTERN in 2015 and NAACOS with DANA in 2012. The presented DOM fluorescence data are smoothed, corrected for instrument drift and calibrated to provide intercomparable data across the sensors. Fluorescence is reported in Raman Units (nm-1), and comparable to laboratory measurements conducted according to current community recommendations.