ALBERT

Description: The measurement of short-lived 223Ra often involves a second measurement for supported activities, which represents 227Ac in the sample. Here we exploit this fact, presenting a set of 284 values on the oceanic distribution of 227Ac, which was collected when analyzing water samples for short-lived radium isotopes by the radium delayed coincidence counting system. The present work compiles 227Ac data from coastal regions all over the northern hemisphere, including values from ground water, from estuaries and lagoons, and from marine end-members. Deep-sea samples from a continental slope off Puerto Rico and from an active vent site near Hawaii complete the overview of 227Ac near its potential sources. The average 227Ac activities of nearshore marine end-members range from 0.4 dpm/m**3 at the Gulf of Mexico to 3.0 dpm m? 3 in the coastal waters of the Korean Strait. In analogy to 228Ra, we find the extension of adjacent shelf regions to play a substantial role for 227Ac activities, although less pronounced than for radium, due to its weaker shelf source. Based on previously published values, we calculate an open ocean 227Ac inventory of 1.35 * 1018 dpm 227Acex in the ocean, which corresponds to 37 moles, or 8.4 kg. This implies a flux of 127 dpm/m**2/y from the deep-sea floor. For the shelf regions, we obtain a global inventory of 227Ac of 4.5 * 10**15 dpm, which cannot be converted directly into a flux value, as the regional loss term of 227Ac to the open ocean would have to be included. Ac has so far been considered to behave similarly to Ra in the marine environment, with the exception of a strong Ac source in the deep-sea due to 231Paex. Here, we present evidence of geochemical differences between Ac, which is retained in a warm vent system, and Ra, which is readily released [Moore, W.S., Ussler, W. and Paull, C.K., 2008-this issue. Short-lived radium isotopes in the Hawaiian margin: Evidence for large fluid fluxes through the Puna Ridge. Marine Chemistry]. Another potential mechanism of producing deviations in 227Ac/228Ra and daughter isotope ratios from the expected production value of lithogenic material is observed at reducing environments, where enrichment in uranium may occur. The presented data here may serve as a reference for including 227Ac in circulation models, and the overview provides values for some end-members that contribute to the global Ac distribution.

Description: This dataset contains hydrographic observations from Sermilik Fjord in SE Greenland, collected in August 2015 aboard the RV Adolf Jensen.

Description: This dataset contains hydrographic observations from Sermilik Fjord in SE Greenland, collected in August 2015 aboard the RV Adolf Jensen, including discrete data derived from water sample analyses and corresponding CTD sensor data. CTD data were collected using a Seabird 25Plus Sealogger equipped with a SBE 43 dissolved oxygen sensor, a Satlantic PAR LOG sensor, and a Wetlabs / Seabird ECO Triplet (chlorophyll-a and CDOM fluorescence, as well as backscattering at 700 nm). Discrete samples for nitrate, phosphate, silicate, and ammonium, were filtered through a sterile 0.22 µM Sterivex filter using standard protocols and kept frozen at -20 °C for later analysis at the Woods Hole Oceanographic Institution Nutrient Analytical Facility. Dissolved nutrient concentrations were quantified using a SEAL AA3 four-channel segmented flow analyzer.

Description: This dataset comprises Radium (Ra), Barium (Ba) and δ18O tracers in addition to chemical constituents (Dissolved Inorganic Carbon (DIC) and Total Alkalinity (AT)) collected during 2015 Canadian GEOTRACES expedition (GN02/GN03) throughout the Canadian Arctic Archipelago aboard the CCGS Amundsen. Included within the dataset are the latitude and longitudes of sampling stations, as well as the sampled depths and the associated basic hydrographic data (T and SP). For every data point, in addition to date and time of collection, the accompanying event, cast and bottle number are recorded as well as GEOTRACES Event ID number. The compilation of this dataset was supported by the Canadian GEOTRACES program as part of the NSERC-CCAR, the U.S. GEOTRACES via NSF Chemical Oceanography (grant no. OCE-1458305), and the DAAD, MOPGA-GRI (grant no.57429828).