Abstract. Freshwater discharge from glaciers is increasing across the Arctic in response to anthropogenic climate change, which raises questions about the potential downstream effects in the marine environment. Whilst a combination of long-term monitoring programmes and intensive Arctic field campaigns have improved our knowledge of glacier–ocean interactions in recent years, especially with respect to fjord/ocean circulation, there are extensive knowledge gaps concerning how glaciers affect marine biogeochemistry and productivity. Following two cross-cutting disciplinary International Arctic Science Committee (IASC) workshops addressing the importance of glaciers for the marine ecosystem, here we review the state of the art concerning how freshwater discharge affects the marine environment with a specific focus on marine biogeochemistry and biological productivity. Using a series of Arctic case studies (Nuup Kangerlua/Godthåbsfjord, Kongsfjorden, Kangerluarsuup Sermia/Bowdoin Fjord, Young Sound and Sermilik Fjord), the interconnected effects of freshwater discharge on fjord–shelf exchange, nutrient availability, the carbonate system, the carbon cycle and the microbial food web are investigated. Key findings are that whether the effect of glacier discharge on marine primary production is positive or negative is highly dependent on a combination of factors. These include glacier type (marine- or land-terminating), fjord–glacier geometry and the limiting resource(s) for phytoplankton growth in a specific spatio-temporal region (light, macronutrients or micronutrients). Arctic glacier fjords therefore often exhibit distinct discharge–productivity relationships, and multiple case-studies must be considered in order to understand the net effects of glacier discharge on Arctic marine ecosystems.

The Mediterranean Sea presents several biogeochemical anomalies compared to the global ocean. An unbalanced N budget, high nitrate/phosphate ratios in subsurface waters and low 15N/14N ratios in particulate and dissolved nitrogen suggest a significant occurrence of N2 fixation. This study presents, for the first time, a basin‐wide overview of direct measurements of N2 fixation, with values in the North Atlantic for comparison, during late spring 2007. Very low N2 fixation rates (0.052 ± 0.031 nmols N l−1d−1) were observed in all sub‐regions of the Mediterranean, in contrast to the higher values measured in the North Atlantic (0.300 ± 0.115 nmols N l−1d−1). Higher phosphorus (inorganic or organic) concentrations were not associated with higher N2 fixation rates. Low 15N/14N ratios in particulate organic nitrogen (from −2.10 to +4.11‰), associated with low N2 fixation rates, suggest that other N sources, such as atmospheric inputs, fuel the Mediterranean ecosystem.

Abstract:The analysis of the mixing processes involving water masses on the Ross Sea continental shelf is one of the goals of the CLIMA project (Climatic Long-term Interactions for the Mass balance in Antarctica). This paper uses extended Optimum MultiParameter analysis (OMP), which is applied to four datasets collected during the cruises of 1994/95, 1995/96, 1997/98 and 2000/01 in the Ross Sea (Antarctica). Data include both hydrological, (temperature, salinity, and pressure; T, S, and P, respectively) and chemical parameters (O 2 , Si(OH) 4 , PO 4 , and NO 3 +NO 2 ). The OMP analysis is based on the assumption that the mixing is a linear process which affects all parameters equally so that each sample shows physical/chemical properties that are the result of the mixing of some properly selected Source Water Types (SWTs). OMP thus evaluates the best set of contributions by all SWTs to each sample, and allows the spatial distribution and structure of the water masses in a basin to be evaluated. Ocean circulation may subsequently be inferred by means of a deeper analysis of the spreading of the water mass. In this study, the "real" Redfield ratios observed in the Ross Sea were used to correct the equations referring to the chemical parameters in accordance with the extended version of OMP. The solutions include some physically realistic constraints. The results allow a detailed description of the water mass distribution, validated through comparison with some "canonical" thermohaline characteristics of the Ross Sea hydrology. In particular our results verify the spreading of the HSSW over the entire continental shelf and emphasize the key role it plays in the ventilation of the deep waters outside the Ross Sea. In addition a description is given of the intrusion of relatively warm waters coming from the open ocean and flowing at some specific locations at the continental shelf break. isobath, runs NW-SE and links the area in front of Cape Adare to Cape Colbeck. Some depressions in the inner area are deeper than the continental shelf break, and therefore behave as reservoirs of the salty and dense waters.The Circumpolar Deep Water (CDW) is carried by the Antarctic Circumpolar Current (ACC) along the boundary of the Ross Sea, following the shelf slope from east to west. CDW strongly influences the thermohaline circulation of this basin, being the only water mass which provides heat to the shelf waters (Jacobs et al. 1985, Locarnini 1994, Jacobs & Giulivi 1998, Gouretsky 1999. In some specific locations it intrudes onto the Ross continental shelf forming, after the interaction with the shelf waters, the modified CDW (MCDW), which can be identified by a subsurface maximum temperature and minimum dissolved oxygen (Jacobs et al. 1985, Locarnini 1994, Budillon et al. 1999.On the western side of the Ross Sea, the physical features of the water column are also affected by the recurring presence of a substantial coastal ice free area, the Terra Nova Bay polynya (Bromwich & Kurtz 1984, Jacobs et al. 1985, Fusco et al. 2...

Abstract. Freshwater discharge from glaciers is increasing across the Artic in response to anthropogenic climate change, which raises questions about the potential downstream effects in the marine environment. Whilst a combination of long-term monitoring programmes and intensive Arctic field campaigns have improved our knowledge of glacier-ocean interactions in recent years, especially with respect to fjord/ocean circulation in the marine environment, there are extensive knowledge gaps concerning how glaciers affect marine biogeochemistry and productivity. Following two cross-cutting disciplinary International Arctic Science Committee (IASC) workshops addressing ‘The importance of glaciers for the marine ecosystem’, here we review the state of the art concerning how freshwater discharge affects the marine environment with a specific focus on marine biogeochemistry and biological productivity. Using a series of Arctic case studies (Nuup Kangerlua/Godthåbsfjord, Kongsfjorden, Bowdoin Fjord, Young Sound, and Sermilik Fjord), the interconnected effects of freshwater discharge on fjord-shelf exchange, nutrient availability, the carbonate system, and the microbial foodweb are investigated. Key findings are that whether the effect of glacier discharge on marine primary production is positive, or negative is highly dependent on a combination of factors. These include glacier type (marine- or land-terminating) and the limiting resource for phytoplankton growth in a specific spatiotemporal region (light, macronutrients or micronutrients). Glacier fjords therefore often exhibit distinct discharge-productivity relationships and multiple case-studies must be considered in order to understand the net effects of glacier discharge on Arctic marine ecosystems.

Abstract. The Mediterranean Sea (MedSea) is considered a "laboratory basin" being an ocean in miniature, suffering dramatic changes in its oceanographic and biogeochemical conditions derived from natural and anthropogenic forces. Moreover, the MedSea is prone to absorb and store anthropogenic carbon due to the particular CO 2 chemistry and the active overturning circulation. Despite this, water column CO 2 measurements covering the whole basin are scarce. This work aims to be a base-line for future studies about the CO 2 system space-time variability in the MedSea combining historic and modern CO 2 cruises in the whole area. Here we provide an extensive vertical and longitudinal description of the CO 2 system variables (total alkalinity -TA, dissolved inorganic carbon -DIC and pH) along an East-West transect and across the Sardinia-Sicily passage in the MedSea from two oceanographic cruises conducted in 2011 measuring CO 2 variables in a coordinated fashion, the RV Meteor M84/3 and the RV Urania EuroFleets 11, respectively. In this sense, we provide full-depth and length CO 2 distributions across the MedSea, and property-property plots showing in each sub-basin post-Eastern Mediterranean Transient (EMT) situation with regard to TA, DIC and pH.The over-determined CO 2 system in 2011 allowed performing the first internal consistency analysis for the particularly warm, high salinity and alkalinity MedSea waters. The CO 2 constants by Mehrbach et al. (1973) refitted by Dickson and Millero (1987) are recommended. The sensitivity of the CO 2 system to the atmospheric CO 2 increase, DIC and/or TA changes is evaluated by means of the Revelle and buffer factors.