Agneta Fransson

Floating ice-algal aggregates below melting arctic sea ice.

During two consecutive cruises to the Eastern Central Arctic in late summer 2012, we observed floating algal aggregates in the melt-water layer below and between melting ice floes of first-year pack ice. The macroscopic (1-15 cm in diameter) aggregates had a mucous consistency and were dominated by typical ice-associated pennate diatoms embedded within the mucous matrix. Aggregates maintained buoyancy and accumulated just above a strong pycnocline that separated meltwater and seawater layers. We were able, for the first time, to obtain quantitative abundance and biomass estimates of these aggregates. Although their biomass and production on a square metre basis was small compared to ice-algal blooms, the floating ice-algal aggregates supported high levels of biological activity on the scale of the individual aggregate. In addition they constituted a food source for the ice-associated fauna as revealed by pigments indicative of zooplankton grazing, high abundance of naked ciliates, and ice amphipods associated with them. During the Arctic melt season, these floating aggregates likely play an important ecological role in an otherwise impoverished near-surface sea ice environment. Our findings provide important observations and measurements of a unique aggregate-based habitat during the 2012 record sea ice minimum year.

Characterization of ikaite (CaCO3•6H2O) crystals in first year Arctic sea ice north of Svalbard

Abstract We identified ikaite crystals (CaCO3 ·6H2O) and examined their shape and size distribution in first-year Arctic pack ice, overlying snow and slush layers during the spring melt onset north of Svalbard. Additional measurements of total alkalinity (TA) were made for melted snow and sea-ice samples. Ikaite crystals were mainly found in the bottom of the snowpack, in slush and the surface layers of the sea ice where the temperature was generally lower and salinity higher than in the ice below. Image analysis showed that ikaite crystals were characterized by a roughly elliptical shape and a maximum caliper diameter of 201.0±115.9 μm (n = 918). Since the ice-melting season had already started, ikaite crystals may already have begun to dissolve, which might explain the lack of a relationship between ikaite crystal size and sea-ice parameters (temperature, salinity, and thickness of snow and ice). Comparisons of salinity and TA profiles for melted ice samples suggest that the precipitation/dissolution of ikaite crystals occurred at the top of the sea ice and the bottom of the snowpack during ice formation/melting processes.

Effect of glacial drainage water on the CO2 system and ocean acidification state in an Arctic tidewater‐glacier fjord during two contrasting years

In order to investigate the effect of glacial water on the CO2 system in the fjord, we studied nthe variability of the total alkalinity (AT), total dissolved inorganic carbon (CT), dissolved inorganic nutrients, noxygen isotopic ratio (d18O), and freshwater fractions from the glacier front to the outer Tempelfjorden on nSpitsbergen in winter 2012 (January, March, and April) and 2013 (April) and summer/fall 2013 (September). nThe two contrasting years clearly showed that the influence of freshwater, mixing, and haline convection naffected the chemical and physical characteristics of the fjord. The seasonal variability showed the lowest ncalcium carbonate saturation state (X) and pH values in March 2012 coinciding with the highest freshwater nfractions. The highest X and pH were found in September 2013, mostly due to CO2 uptake during primary nproduction. Overall, we found that increased freshwater supply decreased X, pH, and AT. On the other nhand, we observed higher AT relative to salinity in the freshwater end-member in the mild and rainy winter nof 2012 (1142 lmol kg21) compared to AT in 2013 (526 lmol kg21). Observations of calcite and dolomite ncrystals in the glacial ice suggested supply of carbonate-rich glacial drainage water to the fjord. This implies nthat winters with a large amount of glacial drainage water partly provide a lessening of further ocean acidification, nwhich will also affect the air-sea CO2 exchange.

Late winter-to-summer change in ocean acidification state in Kongsfjorden, with implications for calcifying organisms

Late winter-to-summer changes (April to July) in ocean acidification state, calcium carbonate (CaCO3) saturation for aragonite (Ωa) and calcite (Ωc) and biogeochemical properties were investigated in 2013 and 2014 in Kongsfjorden, Svalbard. We investigated physical (salinity, temperature) and chemical (carbonate system, nutrient) properties in the water column from the glacier front in the fjord to the west Spitsbergen shelf. The average range of Ωa in the upper 50xa0m in the fjord in winter was 1.59–1.74 and in summer 1.65–2.66. The lowest Ωa (1.5) was close to the reported critical threshold for aragonite-forming organisms such as the pteropod Limacina helicina. In summer 2013, Ωa, pHT and salinity were generally lower than in 2014 as a result of a larger influence of high-CO2 water from the coastal current and less Atlantic water. The inner fjord was influenced by glacial water in summer which decreased Ωa by 0.7. Biological CO2 consumption based on a winter-to summer decrease in nitrate was larger in 2014 than in 2013, suggesting more primary production in 2014. The influence of freshwater decreased Ωa by the same amount as the biological effect increased Ωa. The seasonal increase in temperature only played a minor role on the increase of Ωa. The biological effect showed more inter-annual variability than the effect of freshwater. Based on this study, we suggest that changes in the inflow of different water masses and freshwater directly influence ocean acidification state, but also indirectly affect the biological drivers of carbonate chemistry in the fjord.

Effects of sea‐ice and biogeochemical processes and storms on under‐ice water fCO2 during the winter‐spring transition in the high Arctic Ocean: Implications for sea‐air CO2 fluxes

We performed measurements of carbon dioxide fugacity (fCO2) in the surface water under Arctic sea ice from January to June 2015 during the Norwegian young sea ICE (N-ICE2015) expedition. Over this period, the ship drifted with four different ice floes and covered the deep Nansen Basin, the slopes north of Svalbard and the Yermak Plateau. This unique winter-to-spring dataset includes the first winter-time under-ice water fCO2 observations in this region. The observed under-ice fCO2 ranged between 315 µatm in winter and 153 µatm in spring, hence was undersaturated relative to the atmospheric fCO2. Although the sea ice partly prevented direct CO2 exchange between ocean and atmosphere, frequently occurring leads and breakup of the ice sheet promoted sea-air CO2 fluxes. The CO2 sink varied between 0.3 and 86 mmol C m−2 d−1, depending strongly on the open-water fractions (OW) and storm events. The maximum sea-air CO2 fluxes occurred during storm events in February and June. In winter, the main drivers of the change in under-ice water fCO2 were dissolution of CaCO3 (ikaite) and vertical mixing. In June, in addition to these processes, primary production and sea-air CO2 fluxes were important. The cumulative loss due to CaCO3 dissolution of 0.7 mol C m−2 in the upper 10 m played a major role in sustaining the undersaturation of fCO2 during the entire study. The relative effects of the total fCO2 change due to CaCO3 dissolution was 38%, primary production 26%, vertical mixing 16%, sea-air CO2 fluxes 16%, and temperature and salinity insignificant. This article is protected by copyright. All rights reserved.

CO2-system development in young sea ice and CO2 gas exchange at the ice/air interface mediated by brine and frost flowers in Kongsfjorden, Spitsbergen

Abstract In March and April 2010, we investigated the development of young landfast sea ice in Kongsfjorden, Spitsbergen, Svalbard. We sampled the vertical column, including sea ice, brine, frost flowers and sea water, to determine the CO2 system, nutrients, salinity and bacterial and ice algae production during a 13 day interval of ice growth. Apart from the changes due to salinity and brine rejection, the sea-ice concentrations of total inorganic carbon (C T), total alkalinity (A T), CO2 and carbonate ions (CO3 2–) in melted ice were influenced by dissolution of calcium carbonate (CaCO3) precipitates (25–55 μmol kg-1) and played the largest role in the changes to the CO2 system. The C T values were also influenced by CO2 gas flux, bacterial carbon production and primary production, which had a small impact on the C T. The only exception was the uppermost ice layer. In the top 0.05 m of the ice, there was a CO2 loss of ∼20 μmol kg-1 melted ice (1 mmol m-2) from the ice to the atmosphere. Frost flowers on newly formed sea ice were important in promoting ice-air CO2 gas flux, causing a CO2 loss to the atmosphere of 140-800 μmol kg--1 d-1 melted frost flowers (7-40 mmol m-2 d–1).

Temporal Variability in Surface Water pCO2 in Adventfjorden (West Spitsbergen) With Emphasis on Physical and Biogeochemical Drivers

Seasonal and interannual variability in surface water partial pressure of CO2 (pCO2) and air-sea CO2 fluxes from a West Spitsbergen fjord (IsA Station, Adventfjorden) are presented, and the associated driving forces are evaluated. Marine CO2 system data together with temperature, salinity, and nutrients, were collected at the IsA Station between March 2015 and June 2017. The surface waters were undersaturated in pCO2 with respect to atmospheric pCO2 all year round. The effects of biological activity (primary production/respiration) followed by thermal forcing on pCO2 were the most important drivers on a seasonal scale. The ocean was a sink for atmospheric CO2 with annual air-sea CO2 fluxes of 36 ± 2 and 31 ± 2 g C·m ·year 1 for 2015–2016 and 2016–2017, respectively, as estimated from the month of April. Waters of an Arctic origin dominated in 2015 and were replaced in 2016 by waters of a transformed Atlantic source. The CO2 uptake rates over the period of Arctic origin waters were significantly higher (2 mmol C·m ·day ) than the rates of the Atlantic origin waters of the following year.

Spatiotemporal Variability of Barium in Arctic Sea‐Ice and Seawater

Freshwater export from the Arctic is critical in determining the density of water at sites of North Atlantic deep water formation, which in turn influences the global flux of oceanic heat and nutrients. We need geochemical tracers and high-resolution observations to refine our freshwater budgets and constrain models for future change. The use of seawater barium concentrations in the Arctic Ocean as a freshwater tracer relies on the conservative behavior of barium in seawater; while this has been shown to be an unreliable assumption in Arctic summers, there are a lack of studies observing seasonal progressions. Here, we present barium concentrations from seawater and sea-ice collected during the Norwegian Young Sea ICE expedition from boreal winter into summer. We use other tracers (salinity, oxygen isotopes, and alkalinity) to reconstruct freshwater inputs and calculate a barium ‘‘deficit’’ that can be attributed to nonconservative processes. We locate a deficit in winter when biological production is low, which we attribute to uptake by barite formation associated with old organic matter or by internal sea-ice processes. We also find a significant barium deficit during the early spring bloom, consistent with uptake into organic-matter associated microenvironments. However, in summer, there no strong barium deficit near the surface, despite high biological production and organic carbon standing stocks, perhaps reflecting phytoplankton assemblage changes, and/or rapid internal cycling. Our findings challenge the assumptions surrounding the use of barium as an Arctic freshwater tracer, and highlight the need to improve our understanding of barium in sea-ice environments.

Using natural analogues to investigate the effects of climate change and ocean acidification on Northern ecosystems

Samuel S. P. Rastrick*, Helen Graham, Kumiko Azetsu-Scott, Piero Calosi, Melissa Chierici, Agneta Fransson, Haakon Hop, Jason Hall-Spencer, Marco Milazzo, Peter Thor, and Tina Kutti Institute of Marine Research, PO Box 1870 Nordnes, 5870 Bergen, Norway Ocean Bergen, Espelandvegen 232, Blomsterdalen, Norway Department of Fisheries and Oceans, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada Département de Biologie, Chimie et Géographie, Université du Quebéc à Rimouski, 300 Allée des Ursulines, Rimouski, QC G5L 3A1, Canada Institute of Marine Research, Fram Centre, 9007 Tromsø, Norway University Centre in Svalbard, Longyearbyen, Norway Norwegian Polar Institute, Fram Centre, N-9296 Tromsø, Norway Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic University of Norway, N-9037 Tromsø, Norway Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, Plymouth University, Drake Circus, Plymouth, Devon PL4 8AA, UK Department of Earth and Marine Science, Università degli studi di Palermo, CoNISMa, Via Archirafi 20, I-90123 Palermo, Italy *Corresponding author: tel: þ4747489401; e-mail: samuel.rastrick@imr.no.