Posts Tagged 'Arctic'



Threats to Arctic ecosystems

Pollution, ocean acidification and global warming are all major threats to Arctic ecosystems and are all inextricably linked. Major global air and ocean currents bring pollutants north to the “Arctic sink” where they accumulate over time, affecting ecosystems and wildlife. Meanwhile, carbon pollution from fossil fuels is causing widespread ocean acidification and global warming, which is happening two to three times faster in the Arctic than other regions. While climate change is having direct effects on Arctic ecosystems, the dynamics of pollutants within Arctic ecosystems are also being affected, enhancing pollutant mobility and effects in some cases.

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Marine CO2 system variability in a high arctic tidewater-glacier fjord system, Tempelfjorden, Svalbard

Highlights

• The marine CO2 system was investigated in an Arctic fjord between 2015 and 2017.

• Primary production caused the largest changes observed in pCO2 and the saturation state of aragonite.

• Air-sea CO2 uptake and freshwater release governed the surface pCO2 over the melt season.

• At least a freshwater fraction larger than 50% was needed to provide aragonite undersaturated waters.

• An excess in the salinity normalized DIC, corrected for primary production/respiration, was found in the deepest water.

Abstract

The marine CO2 system in Tempelfjorden (Svalbard) was investigated between August 2015 and December 2017 using total alkalinity, pH, temperature, salinity, oxygen isotopic ratio, and nutrient data. Primary production resulted in the largest changes that were observed in the partial pressure of CO2 (pCO2, 140 μatm) and the saturation state of aragonite (ΩAr, 0.9). Over the period of peak freshwater discharge (June to August), the freshwater addition and air-sea CO2 uptake (on average 15.5 mmol m−2 day−1 in 2017) governed the surface pCO2. About one fourth of the uptake was driven by the freshening. The sensitivity of ΩAr to the freshwater addition was investigated using robust regressions. If the effect of air-sea CO2 exchange was removed from ΩAr, a freshwater fraction larger than 50% (lower range of uncertainty) was needed to provide aragonite undersaturated waters. This study shows that ΩAr and freshwater fraction relationships that are derived from regression techniques and the interpretation thereof are sensitive to the effect of air-sea CO2 exchange. Since the freshening in itself only drives a fraction of the air-sea CO2 uptake, studies that do not account for this exchange will overestimate the impact of freshwater on ΩAr. Finally, in the summer an excess in the salinity normalized dissolved inorganic carbon, corrected for aerobic primary production/respiration, of on average 86 μmol kg−1 was found in the deepest water of the fjord. This excess is suggested to be a result of enhanced CO2 uptake and brine release during the period of sea ice growth.

Continue reading ‘Marine CO2 system variability in a high arctic tidewater-glacier fjord system, Tempelfjorden, Svalbard’

Transport of carbon dioxide and heavy metals from hydrothermal vents to shallow water by hydrate-coated gas bubbles

Deep-sea hydrothermal plumes are of major importance in the biogeochemical ocean cycles and in this study we focus on plumes emitted from the Jan Mayen vent fields in the Norwegian-Greenland Sea. These vent fields are of interest because of the high CO2 concentrations and also due to the different styles of venting occurring here. Venting at these sites occurs between 550 and 700 m depth and is characterized by the release of hydrate coated bubbles as well as focused flow venting. This study aims to enhance our current understanding of the impact of CO2 rich hydrate coated bubbles on the water column as well as the interaction between hydrothermally derived gases and metals in the water column. Three water column surveys were conducted in this area in between 2012 and 2014, in which the non-buoyant plume (NBP) produced by focused flow venting from both the Troll Wall and the Perle & Bruse vent sites was identified by primordial helium (3He), methane (CH4), carbon dioxide (CO2) and dissolved manganese (Mn) enrichments close to 500 m water depth. Our results show that venting of hydrate coated CO2 rich bubbles increases bubble rise height, which results in shallow acidification locally above the vent sites. A polymetallic anomaly in the mid-depth water column above the NBP is also hypothesized to be a result of the hydrate coated bubbles. We argue that nanoparticles get sequestered to the hydrate lattice and travel with the bubbles until the lattice becomes unstable due to gas expansion upon depressurization during ascent. This process could fuel the primary production in the pelagic water column.

Continue reading ‘Transport of carbon dioxide and heavy metals from hydrothermal vents to shallow water by hydrate-coated gas bubbles’

Response of the Arctic marine inorganic carbon system to ice algae and under‐ice phytoplankton blooms: a case study along the fast‐ice edge of Baffin Bay

Past research in seasonally ice‐covered Arctic seas has suggested that ice algae play a role in reducing dissolved inorganic carbon (DIC) during spring, preconditioning surface waters to low dissolved CO2 (pCO2sw), and uptake of atmospheric CO2 during the ice‐free season. The potential role of under‐ice phytoplankton blooms on DIC and pCO2sw has not often been considered. In this study we examined the inorganic carbon system beneath landfast sea ice starting midway through a bottom ice algae bloom and concluding in the early stages of an under‐ice phytoplankton bloom. During most of the ice algae bloom we observed a slight increase in DIC/pCO2sw in surface waters, as opposed to the expected reduction. Biomass calculations confirm that the role of ice algae on DIC/pCO2sw in the study region were minor and that this null result may be widely applicable. During snow melt, we observed an under‐ice phytoplankton bloom (to 10 mg/m3 Chl a) that did reduce DIC and pCO2sw. We conclude that under‐ice phytoplankton blooms are an important biological mechanism that may predispose some Arctic seas to act as a CO2 sink at the time of ice breakup. We also found that pCO2sw was undersaturated at the study location even at the beginning of our sampling period, consistent with several other studies that have measured under‐ice pCO2sw in late winter or early spring. Finally, we present the first measurements of carbonate saturation states for this region, which may be useful for assessing the vulnerability of a local soft‐shelled clam fishery to ocean acidification.

Continue reading ‘Response of the Arctic marine inorganic carbon system to ice algae and under‐ice phytoplankton blooms: a case study along the fast‐ice edge of Baffin Bay’

Warming and CO2 enhance Arctic heterotrophic microbial activity

Ocean acidification and warming are two main consequences of climate change that can directly affect biological and ecosystem processes in marine habitats. The Arctic Ocean is the region of the world experiencing climate change at the steepest rate compared with other latitudes. Since marine planktonic microorganisms play a key role in the biogeochemical cycles in the ocean it is crucial to simultaneously evaluate the effect of warming and increasing CO2 on marine microbial communities. In 20 L experimental microcosms filled with water from a high-Arctic fjord (Svalbard), we examined changes in phototrophic and heterotrophic microbial abundances and processes [bacterial production (BP) and mortality], and viral activity (lytic and lysogenic) in relation to warming and elevated CO2. The summer microbial plankton community living at 1.4°C in situ temperature, was exposed to increased CO2 concentrations (135–2,318 μatm) in three controlled temperature treatments (1, 6, and 10°C) at the UNIS installations in Longyearbyen (Svalbard), in summer 2010. Results showed that chlorophyll a concentration decreased at increasing temperatures, while BP significantly increased with pCO2 at 6 and 10°C. Lytic viral production was not affected by changes in pCO2 and temperature, while lysogeny increased significantly at increasing levels of pCO2, especially at 10°C (R2 = 0.858, p = 0.02). Moreover, protistan grazing rates showed a positive interaction between pCO2 and temperature. The averaged percentage of bacteria grazed per day was higher (19.56 ± 2.77% d-1) than the averaged percentage of lysed bacteria by virus (7.18 ± 1.50% d-1) for all treatments. Furthermore, the relationship among microbial abundances and processes showed that BP was significantly related to phototrophic pico/nanoflagellate abundance in the 1°C and the 6°C treatments, and BP triggered viral activity, mainly lysogeny at 6 and 10°C, while bacterial mortality rates was significantly related to bacterial abundances at 6°C. Consequently, our experimental results suggested that future increases in water temperature and pCO2 in Arctic waters will produce a decrease of phytoplankton biomass, enhancement of BP and changes in the carbon fluxes within the microbial food web. All these heterotrophic processes will contribute to weakening the CO2 sink capacity of the Arctic plankton community.

Continue reading ‘Warming and CO2 enhance Arctic heterotrophic microbial activity’

The internal consistency of the marine carbon dioxide system for high latitude shipboard and in situ monitoring

Highlights
• Best calculations from combination of T,P-dependent and non-dependent parameters

• The dissociation constants of M73 and L yielded the best internal consistency

• Monte Carlo simulation of uncertainty propagation shows combined uncertainty to be more dependent on input parameters, less on dissociation constants

• Internal consistency study for deep ocean conditions is required

Abstract
Deep convection in the Labrador Sea supplies large amounts of anthropogenic carbon to the ocean’s interior. We use measurements of all four measurable CO2 system parameters made along AR7W (across Labrador Sea) between 2013 and 2015 to assess the internal consistency of the carbonate system, including, as appropriate, conversion to in situ temperature (T) and pressure (P). The best agreement between measured and calculated values was obtained through combination of T,P-dependent (pH or pCO2) and non-dependent (TA or DIC) parameters. Use of the dissociation constants of Mehrbach et al. (1973) as refit by Dickson and Millero (1987) and Lueker et al. (2000) yielded the best internal consistency irrespective of the input parameters used. A Monte Carlo simulation demonstrated that the propagated uncertainty (i.e. combined standard uncertainty) of calculated parameters of the carbonate system is (a) always larger than the analytical precision of the measurements themselves; (b) strongly dependent on the choice of input parameters and uncertainties; (c) less dependent on choice of the specific set of constants. For calculation of other parameters of the carbonate system from TA and DIC measurements made throughout the Labrador Sea time-series, the estimated combined standard uncertainty of calculated pCO2 and pH based on the Monte Carlo simulation is ~ 13 μatm and ~ 0.012 pH units respectively, with accuracy relative to laboratory-based measurement estimated to be between −3 and − 13 μatm and 0.002 and 0.007 pH units. Internal consistency especially at in situ temperature and pressure conditions is important for rapidly developing sensor-based monitoring programs in the region, including measurement of pH and/or pCO2 from gliders, profiling floats and moorings. We highlight uncertainty associated with the large pressure effect on pH and pCO2, and recommend a study of carbonate system internal consistency under deep ocean conditions that addresses pressure effects on calculations.

Continue reading ‘The internal consistency of the marine carbon dioxide system for high latitude shipboard and in situ monitoring’

Climate in Svalbard 2100 – a knowledge base for climate adaptation

This report was commissioned by the Norwegian Environment Agency in order to provide basic information for climate change effect studies and climate change adaptation in Svalbard. It includes descriptions of historical, as well as projections for future climate development in the atmosphere, hydrosphere, cryosphere and ocean, and it includes effects on the physical nature, e.g. risks associated with landslides and avalanches. The projections for future climate are based on the global climate models used in the IPCCs fifth assessment report (IPCC, 2013). Dependent on availability of model data, three scenarios for emissions of greenhouse gases are used: “RCP8.5” (“business as usual”; “high emissions”), “RCP4.5” (reductions after 2040; “medium emissions”) and “RCP2.6” (drastic cuts from 2020; “low emissions”). Climate change in the atmosphere and land surface are projected up to the year 2100 and in the ocean up to the year 2070.

The report is to a large degree an assessment of existing literature and model results, e.g. the Arctic CORDEX regional climate models. In addition, a fine scale atmospheric regional climate model (COSMO-CLM) has been run, and the results were applied for estimating changes in e.g. heavy rainfall, frost days, snow, permafrost and glaciers. Further, a hydrological model has been run for Svalbard for present and projected future climate, based on input data from Arctic CORDEX. Also for the ocean, new analyses have been performed, based on the best available model data. Below follows a summary based on a combination of the assessment and results from new analyses.

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