Posts Tagged 'Arctic'

The role of river runoff in the Kara Sea surface layer acidification and carbonate system changes

This study aims to perform the results of the investigation of the Kara Sea carbonate system changes and the factors that determine it. The important feature of the Kara Sea water structure is strong stratification caused mainly by the Ob’ and Yenisey rivers discharge which is estimated as 81% of the total continental runoff to the sea. Occurring climate changes, as an increase in the total volume of the Arctic Ocean water (due to melting of glaciers, sea ice decline and river runoff increase), air temperature and CO2 concentration growth should affect greatly the Kara Sea carbonate system. However, riverine water influence seems to be the main driver of future acidification of the Kara Sea water due to permafrost thawing as it stores a great amount of buried carbon. An increase of carbon (mainly inorganic) flow to the sea will lead to carbonate equilibrium shift, oxidation of organic matter and release of CO2 that ultimately leads to a decrease in pH and therefore acidification. The area of the riverine plume depends on the amount of freshwater flowing into the sea and the conditions of the wind forcing. According to the data from Shirshov Institute cruises within the plume area aragonite saturation is below 1 that shows its state as acidified. Prevalence of pCO2 values in the freshened surface layer over the atmospheric shows that atmospheric carbon dioxide, apparently, cannot serve as the main driver for the acidification of the surface waters of the Kara Sea. At the shallow shelf to the north of the Ob’ Inlet mouth we observe acidification of the whole water column from surface to the bottom layer due to elevated riverine discharge and increase of flowing terrestrial carbon.

Continue reading ‘The role of river runoff in the Kara Sea surface layer acidification and carbonate system changes’

Net community production and carbon exchange from winter to summer in the Atlantic Water inflow to the Arctic Ocean

The eastern Fram Strait and area north of Svalbard, are influenced by the inflow of warm Atlantic water, which is high in nutrients and CO2, influencing the carbon flux into the Arctic Ocean. However, these estimates are mainly based on summer data and there is still doubt on the size of the net ocean Arctic CO2 sink. We use data on carbonate chemistry and nutrients from three cruises in 2014 in the CarbonBridge project (January, May, and August) and one in Fram Strait (August). We describe the seasonal variability and the major drivers explaining the inorganic carbon change (CDIC) in the upper 50 m, such as photosynthesis (CBIO), and air-sea CO2 exchange (CEXCH). Remotely sensed data describes the evolution of the bloom and net community production. The focus area encompasses the meltwater-influenced domain (MWD) along the ice edge, the Atlantic water inflow (AWD), and the West Spitsbergen shelf (SD). The CBIO total was 2.2 mol C m–2 in the MWD derived from the nitrate consumption between January and May. Between January and August, the CBIO was 3.0 mol C m–2 in the AWD, thus CBIO between May and August was 0.8 mol C m–2. The ocean in our study area mainly acted as a CO2 sink throughout the period. The mean CO2 sink varied between 0.1 and 2.1 mol C m–2 in the AWD in August. By the end of August, the AWD acted as a CO2 source of 0.7 mol C m–2, attributed to vertical mixing of CO2-rich waters and contribution from respiratory CO2 as net community production declined. The oceanic CO2 uptake (CEXCH) from the atmosphere had an impact on CDIC between 5 and 36%, which is of similar magnitude as the impact of the calcium carbonate (CaCO3, CCALC) dissolution of 6–18%. CCALC was attributed to be caused by a combination of the sea-ice ikaite dissolution and dissolution of advected CaCO3 shells from the south. Indications of denitrification were observed, associated with sea-ice meltwater and bottom shelf processes. CBIO played a major role (48–89%) for the impact on CDIC.

Continue reading ‘Net community production and carbon exchange from winter to summer in the Atlantic Water inflow to the Arctic Ocean’

Arctic sensitivity? Suitable habitat for benthic taxa is surprisingly robust to climate change

Arctic marine ecosystems are often assumed to be highly vulnerable to ongoing climate change, and are expected to undergo significant shifts in structure and function. Community shifts in benthic fauna are likely to result from changes in key physico-chemical drivers, such as ocean warming, but there is little ecological data on most Arctic species to support any specific predictions as to how vulnerable they are, or how future communities may be structured. We used a species distribution modeling approach (MaxEnt) to project changes over the 21st century in suitable habitat area for different species of benthic fauna by combining presence observations from the OBIS database with environmental data from a coupled climate-ocean model (SINMOD). Projected mean % habitat losses over taxonomic groups were small (0–11%), and no significant differences were found between Arctic, boreal, or Arcto-boreal groups, or between calcifying and non-calcifying groups. However, suitable habitat areas for 14 of 78 taxa were projected a change by over 20%, and several of these taxa are characteristic and/or habitat-forming fauna on some Arctic shelves, suggesting a potential for significant ecosystem impacts. These results highlight the weakness of general statements regarding vulnerability of taxa on biogeographic or presumed physiological grounds, and suggest that more basic biological data on Arctic taxa are needed for improved projections of ecosystem responses to climate change.

Continue reading ‘Arctic sensitivity? Suitable habitat for benthic taxa is surprisingly robust to climate change’

The Arctic picoeukaryote Micromonas pusilla benefits from ocean acidification under constant and dynamic light

Compared to the rest of the globe, the Arctic Ocean is affected disproportionately by climate change. Despite these fast environmental changes, we currently know little about the effects of ocean acidification (OA) on marine key species in this area. Moreover, the existing studies typically test the effects of OA under constant, hence artificial light fields. In this study, the abundant Arctic picoeukaryote Micromonas pusilla was acclimated to current (400 μatm) and future (1000 μatm) pCO2 levels under a constant as well as dynamic light, simulating natural light fields as experienced in the upper mixed layer. To describe and understand the responses to these drivers, growth, particulate organic carbon (POC) production, elemental composition, photophysiology and reactive oxygen species (ROS) production were analysed. M. pusilla was able to benefit from OA on various scales, ranging from an increase in growth rates to enhanced photosynthetic capacity, irrespective of the light regime. These beneficial effects were, however, not reflected in the POC production rates, which can be explained by energy partitioning towards cell division rather than biomass build-up. In the dynamic light regime, M. pusilla was able to optimise its photophysiology for effective light usage during both low and high light periods. This effective photoacclimation, which was achieved by modifications to photosystem II (PSII), imposed high metabolic costs leading to a reduction in growth and POC production rates when compared to constant light. There were no significant interactions observed between dynamic light and OA, indicating that M. pusilla was able maintain effective photoacclimation without increased photoinactivation under high pCO2. Based on these findings, physiologically plastic M. pusilla may exhibit a robust positive response to future Arctic Ocean conditions.

Continue reading ‘The Arctic picoeukaryote Micromonas pusilla benefits from ocean acidification under constant and dynamic light’

Factors regulating nitrification in the Arctic Ocean: potential impact of sea ice reduction and ocean acidification

Nitrification is susceptible to changes in light and pH and, thus, could be influenced by recent sea ice reductions and acidification in the Arctic Ocean. We investigated the sensitivity of nitrification to light, pH, and substrate availability in a natural nitrifier community of the Arctic Ocean. Nitrification was active near the bottom of the shelf region (250 m). In pH control experiments, nitrification rates significantly declined when the pH was manipulated to be 0.22 lower than the controls. However, nitrification was relatively insensitive to changes in pH compared to changes in light. Light control experiments showed that nitrification was inhibited by a light intensity above 0.11 mol photons m−2 day−1, which was presumably the light threshold. A light intensity greater than the light threshold extended to the shelf bottom and upper halocline layer, limiting nitrification in these waters. Satellite data analyses indicated that the area where light levels inhibit nitrification has increased throughout the Arctic Ocean due to the recent sea ice reduction, which may lead to a declining trend in nitrification. Our results suggest that stronger light levels in the future Arctic Ocean could further suppress nitrification and alter the composition of inorganic nitrogen, with implications for the structure of ecosystems.

Continue reading ‘Factors regulating nitrification in the Arctic Ocean: potential impact of sea ice reduction and ocean acidification’

Episodic Arctic CO2 limitation in the west Svalbard shelf

The European Sector of the Arctic Ocean is characterized by low CO2 concentrations in seawater during spring and summer, largely due to strong biological uptake driven by extensive plankton blooms in spring. The spring plankton bloom is eventually terminated by nutrient depletion and grazing. However, low CO2 concentrations in seawater and low atmospheric resupply of CO2 can cause episodes during which the phytoplankton growth is limited by CO2. Here, we show that gross primary production (GPP) of Arctic plankton communities increases from 32 to 72% on average with CO2 additions in spring. Enhanced GPP with CO2 additions occur during episodes of high productivity, low CO2 concentration and in the presence of dissolved inorganic nutrients. However, during summer the addition of CO2 supresses planktonic Arctic GPP. Events of CO2 limitation in spring may contribute to the termination of the Arctic spring plankton blooms. The stimulation of GPP by CO2 during the spring bloom provides a biotic feedback loop that might influence the global role played by the Arctic Ocean as a CO2 sink in the future.

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Evaluating present and future potential of arctic fisheries in Canada

Highlights

• Climate change will increase access to Arctic marine fish stocks in Canada.

• Projections show positive increases in fisheries catch and value potential with climate change.

• Range shifts driven by ocean warming will lead to increased catch potential.

• Ocean acidification may reduce projected increase in catch potential.

• Ecological, economic, social and cultural impacts of exploitation must be considered.

Abstract

The Arctic remains one of the most pristine marine regions in the world, however climate change and increasing favourable conditions is triggering increasing exploration and development of commercial fisheries. Canada’s Arctic marine capture fisheries are currently small relative to fisheries in other regions in Canada but small scale, predominantly Inuit fisheries are more wide spread. In this study, catch data was first used to estimate the current state of Arctic marine fisheries. Next, an integrated modelling approach was used to estimate the current and future fisheries potentials under high and low climate change scenarios. Comparisons of the current (2004–2015) annual reported tonnage and modelled estimates (±standard deviation) suggest that annual sustainable fisheries catch potential could be much greater at 4.07 (±2.86) million tonnes than the current catch of 189 (±6.26) thousand tonnes. Under a high climate change scenario, future (2091–2100) fisheries potential was projected to increase to 6.95 (±5.07) million tonnes of catch, while under low climate change scenario catch potential was similar to estimates of current catch potential. However, the greatest source of variance in catch potential estimates came from parameter uncertainty, followed by scenario and model uncertainty. These results contribute to understanding Canada’s Arctic marine ecosystems in the face of a rapidly changing environment, yet proper steps must be taken to ensure cultural preservation for Inuit communities as well as ecological, economic, and social sustainability.

Continue reading ‘Evaluating present and future potential of arctic fisheries in Canada’


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Ocean acidification in the IPCC AR5 WG II

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