Description: A total of 125 aerosol samples were analysed for their lithium concentrations and deposition flux. Daily aerosol samples were collected from the Pacific Ocean during CLIVAR-CO2 Repeat Hydrography Sections P16 and P2. The P16 section follows 150°-152°W and was divided into two legs, a southern leg from 17°S to 71°S in January-February 2005, and a northern leg from 16°S to 56°N in February-March 2006. CLIVAR-CO2 section P2 from Japan to San Diego, along 30°N, was visited in June-August 2004. The aerosol data from both CLIVAR-CO2 sections include aerosol lithium concentration measured following digestion in HF:HNO3:HCl mixture and corrected for sea-salt contributions (Li xs total), the P16 data also includes aerosol lithium extracted with ultrapure deionised water (≥18 MΩ) by pulling 100 mL of deionised water within ten seconds through the filter (Li xs MQ). Aerosol lithium deposition flux was calculated based on the local rain rate.

Description: A detailed survey of a high Arctic fjord (Kongsfjorden, Svalbard),subjected to a large glacier discharge, was carried out from 24 July to 13 August 2016. Field activities addressed the identification ofthe effects of glacier and iceberg melting on the evolution of nutrient, dissolved organic matter and carbonate systems in this coastal marine environment. Complete CTD profiles were collected in 60 marine stations in theinner area of Kongsfjorden, during six oceanographic surveys, by means of CTD downcasts. CTD profiles were acquired with a Seabird 19plus SeaCATprofiler, equipped with a TURNER Cyclops turbidimeter.

Description: This dataset contains measured labile particulate and total particulate trace element concentrations (Al, Ti, V, P, Fe, Mn, Co, Ni, Cu, and Cd) of water bottle samples collected during GEOTRACES expedition GN05 (PS100) between 21 July and 1 September 2016 on Northeast Greenland Shelf. Samples were collected using the ultra-clean CTD rosette, equipped with 24 × 12 L GoFlo bottles following GEOTRACES sampling protocols (Cutter et al., 2017; https://www.geotraces.org). Particulate TM samples were collected onto pre-acid leached Polyethersulfone (PES) Membrane filters (0.2 µm, Sartorius) with 1.2 - 4.1 L of seawater filtered per sample. Labile particulates were determined after applying a weak acid leach with a mild reducing agent and a short heating step with a total leach time of 2 h. Total particulates were then analyzed following a 15 h reflux digest at 150 °C using a mixture of hydrofluoric acid and nitric acid. The validation of labile and total particulate trace metal analyses was monitored by reference materials BCR-414 and PACS-3. Information on the analytical procedure including reference materials and limits of detection can be found in related published manuscripts. The concentrations reflect the mean and the corresponding uncertainty is calculated as the standard deviation to replicate measurements. Uncertainty is calculated as one standard deviation (1σ, STD) to replicate measurements via ICP-MS. Use of quality flags (QF) according to GEOTRACES policy (https://www.geotraces.org/geotraces-quality-flag-policy/).

Description: Concentrations of heme b were determined in a mesocosm experiment situated in Gullmar Fjord off Sweden. The mesocosm experiment lasted for ca. one hundred days and was characterised by the growth of a primary nutrient replete and a secondary nutrient deplete phytoplankton bloom. Heme b varied between 40 ± 10 pmol/l in the prebloom period up to a maximum of 700 ± 400 pmol/l just prior to the time of the primary chlorophyll a maximum. Thereafter, heme b concentrations decreased again to an average of 120 ± 60 pmol/l. When normalised to total particulate carbon, heme b was most abundant during the initiation of the nutrient replete spring bloom, when ratios reached 52 ± 24 µmol/mol; ten times higher than values observed both pre and post the primary bloom. Concentrations of heme b correlated with those of chlorophyll a. Nevertheless, differences were observed in the relative concentrations of the two parameters, with heme b concentrations increasing relative to chlorophyll a during the growth of the primary bloom, decreasing over the period of the secondary bloom and increasing again through the latter period of the experiment. Heme b abundance was therefore influenced by nutrient concentrations and also likely by changing community composition. In half of the mesocosms, pCO2 was elevated and maintained at ca.1000 µatm, however we observed no significant differences between heme b in plus or ambient pCO2 mesocosms, either in absolute terms, or relative to total particulate carbon and chlorophyll a. The results obtained in this study contribute to our understanding of the distribution of this significant component of the biogenic iron pool, and provide an iron replete coastal water end member that aids the interpretation of the distributions of heme b in more iron deplete open ocean waters.

Description: Inorganic nitrogen depletion restricts productivity in much of the low-latitude oceans, generating a selective advantage for diazotrophic organisms capable of fixing atmospheric dinitrogen (N2). However, the abundance and activity of diazotrophs can in turn be controlled by the availability of other potentially limiting nutrients, including phosphorus (P) and iron (Fe). Here we present high-resolution data (~0.3°) for dissolved iron, aluminum, and inorganic phosphorus that confirm the existence of a sharp north-south biogeochemical boundary in the surface nutrient concentrations of the (sub)tropical Atlantic Ocean. Combining satellite-based precipitation data with results from a previous study, we here demonstrate that wet deposition in the region of the intertropical convergence zone acts as the major dissolved iron source to surface waters. Moreover, corresponding observations of N2 fixation and the distribution of diazotrophic Trichodesmium spp. indicate that movement in the region of elevated dissolved iron as a result of the seasonal migration of the intertropical convergence zone drives a shift in the latitudinal distribution of diazotrophy and corresponding dissolved inorganic phosphorus depletion. These conclusions are consistent with the results of an idealized numerical model of the system. The boundary between the distinct biogeochemical systems of the (sub)tropical Atlantic thus appears to be defined by the diazotrophic response to spatial-temporal variability in external Fe inputs. Consequently, in addition to demonstrating a unique seasonal cycle forced by atmospheric nutrient inputs, we suggest that the underlying biogeochemical mechanisms would likely characterize the response of oligotrophic systems to altered environmental forcing over longer timescales.