scholarly journals Impacts of ikaite export from sea ice to the underlying seawater in a sea ice-seawater mesocosm

2016 ◽  
Author(s):  
N.-X Geilfus ◽  
R. J. Galley ◽  
B. G. T. Else ◽  
T. Papakyriakou ◽  
O. Crabeck ◽  
...  
Keyword(s):  
Sea Ice ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Open Water ◽  
Carbon Dynamics ◽  
Co2 Exchange ◽  
Total Alkalinity ◽  
Main Process ◽  
Saturation State ◽  
Ice Growth

Abstract. Ikaite precipitation within sea ice could act as a significant sink for atmospheric CO2. However, the fate of these ikaite crystals is still poorly understood. We quantify temporal inorganic carbon dynamics from initial sea ice formation from open water to its melt during a month-long experiment in a sea ice-seawater mesocosm pool. Within sea ice, ikaite precipitation and CO2 exchange with the atmosphere were the main processes affecting inorganic carbon dynamics, while the dissolution of ikaite was the main process affecting inorganic carbon dynamics in the underlying seawater. Based on the total alkalinity (TA) and total dissolved inorganic carbon (TCO2) within sea ice and seawater, we estimated ikaite precipitated up to 167 ± 3 µmol kg-1 within sea ice; up to 57 % of the ikaite precipitated within sea ice was exported to the underlying seawater where it was dissolved. Ikaite export from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased sea ice vertical connectivity due to the upward percolation of seawater, and meltwater flushing during sea ice melt. The dissolution of the ikaite crystals in the water column kept the seawater pCO2 undersaturated compared to the atmosphere in spite of increased salinity, TA, and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state (Ωaragonite) in fall and winter in ice-covered areas, at the time when Ωaragonite is smallest.

scholarly journals Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

2016 ◽  
Vol 10 (5) ◽  
pp. 2173-2189 ◽  
Author(s):  
Nicolas-Xavier Geilfus ◽  
Ryan J. Galley ◽  
Brent G. T. Else ◽  
Karley Campbell ◽  
Tim Papakyriakou ◽  
...  
Keyword(s):  
Sea Ice ◽  
Water Column ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Carbon Dynamics ◽  
Total Alkalinity ◽  
Main Process ◽  
Saturation State ◽  
Ice Growth ◽  
Ice Melt

Abstract. The precipitation of ikaite and its fate within sea ice is still poorly understood. We quantify temporal inorganic carbon dynamics in sea ice from initial formation to its melt in a sea ice–seawater mesocosm pool from 11 to 29 January 2013. Based on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO2), the main processes affecting inorganic carbon dynamics within sea ice were ikaite precipitation and CO2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea ice acted as an active layer, releasing CO2 to the atmosphere during the growth phase, taking up CO2 as it melted and exporting both ikaite and TCO2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 µmolkg−1 within sea ice was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64–66 µmolkg−1 in the water column. The export of TCO2 from sea ice to the water column increased the underlying seawater TCO2 by 43.5 µmolkg−1, suggesting that almost all of the TCO2 that left the sea ice was exported to the underlying seawater. The export of ikaite from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased vertical connectivity in sea ice due to the upward percolation of seawater and meltwater flushing during sea ice melt. Based on the change in TA in the water column around the onset of sea ice melt, more than half of the total ikaite precipitated in the ice during sea ice growth was still contained in the ice when the sea ice began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state (Ωaragonite) in fall and in winter in ice-covered areas, at the time when Ωaragonite is smallest.

scholarly journals Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

2017 ◽  
Author(s):  
Jacoba Mol ◽  
Helmuth Thomas ◽  
Paul G. Myers ◽  
Xianmin Hu ◽  
Alfonso Mucci
Keyword(s):  
Sea Ice ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Beaufort Sea ◽  
Total Alkalinity ◽  
The Arctic ◽  
Surface Mixed Layer ◽  
Saturation State ◽  
Carbon Transfer ◽  
Mackenzie Shelf

Abstract. The Mackenzie Shelf in the southeastern Beaufort Sea is a region that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries inorganic carbon and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world oceans. Upwelling carries dissolved inorganic carbon (DIC) and nutrient-rich waters from the Pacific-origin upper halocline layer (UHL) onto the shelf. Profiles of DIC and total alkalinity (TA) taken in August and September of 2014 are used to investigate the cycling of inorganic carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of inorganic carbon are quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4) configuration of the Nucleus of European Modelling of the Ocean (NEMO) framework. A strong upwelling event prior to sampling on the Mackenzie Shelf is analyzed and the resulting influence on the carbonate system, including the saturation state of waters with respect to aragonite and pH, is investigated. TA and the oxygen isotope ratio of water (δ18O) are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air-sea fluxes of carbon dioxide (CO2) in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis for understanding how it will respond to the aforementioned climate-induced changes.

scholarly journals CO<sub>2</sub> perturbation experiments: similarities and differences between dissolved inorganic carbon and total alkalinity manipulations

2009 ◽  
Vol 6 (10) ◽  
pp. 2145-2153 ◽  
Author(s):  
K. G. Schulz ◽  
J. Barcelos e Ramos ◽  
R. E. Zeebe ◽  
U. Riebesell
Keyword(s):  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Calcium Carbonate Precipitation ◽  
Carbonate Chemistry ◽  
Carbonate System ◽  
Experimental Conditions ◽  
Saturation State ◽  
Basic Approaches

Abstract. Increasing atmospheric carbon dioxide (CO2) through human activities and invasion of anthropogenic CO2 into the surface ocean alters the seawater carbonate chemistry, increasing CO2 and bicarbonate (HCO3−) at the expense of carbonate ion (CO32−) concentrations. This redistribution in the dissolved inorganic carbon (DIC) pool decreases pH and carbonate saturation state (Ω). Several components of the carbonate system are considered potential key variables influencing for instance calcium carbonate precipitation in marine calcifiers such as coccolithophores, foraminifera, corals, mollusks and echinoderms. Unravelling the sensitivities of marine organisms and ecosystems to CO2 induced ocean acidification (OA) requires well-controlled experimental setups and accurate carbonate system manipulations. Here we describe and analyse the chemical changes involved in the two basic approaches for carbonate chemistry manipulation, i.e. changing DIC at constant total alkalinity (TA) and changing TA at constant DIC. Furthermore, we briefly introduce several methods to experimentally manipulate DIC and TA. Finally, we examine responses obtained with both approaches using published results for the coccolithophore Emiliania huxleyi. We conclude that under most experimental conditions in the context of ocean acidification DIC and TA manipulations yield similar changes in all parameters of the carbonate system, which implies direct comparability of data obtained with the two basic approaches for CO2 perturbation.

scholarly journals Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

2018 ◽  
Vol 15 (4) ◽  
pp. 1011-1027 ◽  
Author(s):  
Jacoba Mol ◽  
Helmuth Thomas ◽  
Paul G. Myers ◽  
Xianmin Hu ◽  
Alfonso Mucci
Keyword(s):  
Sea Ice ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Beaufort Sea ◽  
Total Alkalinity ◽  
The Arctic ◽  
Surface Mixed Layer ◽  
Carbon Transfer ◽  
Mackenzie Shelf ◽  
Upwelling Event

Abstract. The Mackenzie Shelf in the southeastern Beaufort Sea is a region that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries dissolved inorganic carbon (DIC) and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world's oceans. Upwelling carries DIC and nutrient-rich waters from the Pacific-origin upper halocline layer (UHL) onto the shelf. Profiles of DIC and total alkalinity (TA) taken in August and September of 2014 are used to investigate the cycling of carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of DIC are quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4) configuration of the Nucleus of European Modelling of the Ocean (NEMO) framework. A strong upwelling event prior to sampling on the Mackenzie Shelf took place, bringing CO2-rich (elevated pCO2) water from the UHL onto the shelf bottom. The maximum on-shelf DIC flux was estimated at 16.9×103 mol C d−1 m−2 during the event. The maximum on-shelf transport of DIC through the upwelling event was found to be 65±15×10-3 Tg C d−1. TA and the oxygen isotope ratio of water (δ18O-H2O) are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air–sea fluxes of carbon dioxide (CO2) in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis for understanding how it will respond to the aforementioned climate-induced changes.

scholarly journals A year in the life of a central California kelp forest: physical and biological insights into biogeochemical variability

2016 ◽  
Author(s):  
David A. Koweek ◽  
Kerry J. Nickols ◽  
Paul R. Leary ◽  
Steve Y. Litvin ◽  
Tom W. Bell ◽  
...  
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Kelp Forest ◽  
Total Alkalinity ◽  
Kelp Forests ◽  
Saturation State ◽  
Central California ◽  
High Co2 ◽  
Spatial Gradients ◽  
Spatially Distributed

Abstract. Kelp forests are among the world's most productive marine ecosystems, yet little is known about their biogeochemistry. This study presents a fourteen-month time series (July 2013–August 2014) of surface and benthic dissolved inorganic carbon and total alkalinity measurements, along with accompanying hydrographic measurements, from six locations within a central California kelp forest. We present ranges and patterns of variability in carbonate chemistry, including pH (7.70–8.33), pCO2 (172–952 µatm), and the aragonite saturation state, ΩAr (0.94–3.91). Surface-to-bottom gradients in CO2 system chemistry were as large as the spatial gradients throughout the bottom of the kelp forest. Dissolved inorganic carbon variability was the main driver of the observed CO2 system variability. The majority of spatial variability in the kelp forest can be explained by advection of cold, dense high CO2 waters into the bottom of the kelp forest, with deeper sites experiencing high CO2 conditions more frequently. Despite the strong imprint of advection on the biogeochemical variability of the kelp forest, surface waters were undersaturated with CO2 in the spring through fall, indicative of the strong role of photosynthesis on biogeochemical variability. We emphasize the importance of spatially distributed measurements for developing a process-based understanding of kelp forest ecosystem function in a changing climate.

scholarly journals Seasonal marine carbon system processes in an Arctic coastal landfast sea ice environment observed with an innovative underwater sensor platform

Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
P. J. Duke ◽  
B. G. T. Else ◽  
S. F. Jones ◽  
S. Marriot ◽  
M. M. M. Ahmed ◽  
...  
Keyword(s):  
Sea Ice ◽  
Phytoplankton Bloom ◽  
Dissolved Inorganic Carbon ◽  
Set Covering ◽  
The Arctic ◽  
Data Set ◽  
Saturation State ◽  
Ice Growth ◽  
Sensor Platform ◽  
Carbon System

Studying carbon dioxide in the ocean helps to understand how the ocean will be impacted by climate change and respond to increasing fossil fuel emissions. The marine carbonate system is not well characterized in the Arctic, where challenging logistics and extreme conditions limit observations of atmospheric CO2 flux and ocean acidification. Here, we present a high-resolution marine carbon system data set covering the complete cycle of sea-ice growth and melt in an Arctic estuary (Nunavut, Canada). This data set was collected through three consecutive yearlong deployments of sensors for pH and partial pressure of CO2 in seawater (pCO2sw) on a cabled underwater observatory. The sensors were remarkably stable compared to discrete samples: While corrections for offsets were required in some instances, we did not observe significant drift over the deployment periods. Our observations revealed a strong seasonality in this marine carbon system. Prior to sea-ice formation, air–sea gas exchange and respiration were the dominant processes, leading to increasing pCO2sw and reduced aragonite saturation state (ΩAr). During sea-ice growth, water column respiration and brine rejection (possibly enriched in dissolved inorganic carbon, relative to alkalinity, due to ikaite precipitation in sea ice) drove pCO2sw to supersaturation and lowered ΩAr to &lt; 1. Shortly after polar sunrise, the ecosystem became net autotrophic, returning pCO2sw to undersaturation. The biological community responsible for this early switch to autotrophy (well before ice algae or phytoplankton blooms) requires further investigation. After sea-ice melt initiated, an under-ice phytoplankton bloom strongly reduced aqueous carbon (chlorophyll-a max of 2.4 µg L–1), returning ΩAr to &gt; 1 after 4.5 months of undersaturation. Based on simple extrapolations of anthropogenic carbon inventories, we suspect that this seasonal undersaturation would not have occurred naturally. At ice breakup, the sensor platform recorded low pCO2sw (230 µatm), suggesting a strong CO2 sink during the open water season.

scholarly journals Air-ice carbon pathways inferred from a sea ice tank experiment

Elem Sci Anth ◽  
2016 ◽  
Vol 4 ◽  
Author(s):  
Marie Kotovitch ◽  
Sébastien Moreau ◽  
Jiayun Zhou ◽  
Martin Vancoppenolle ◽  
Gerhard S. Dieckmann ◽  
...  
Keyword(s):  
Sea Ice ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Bubble Nucleation ◽  
Atmospheric Co2 ◽  
The Arctic ◽  
Gas Bubble ◽  
Co2 Fluxes ◽  
Carbon Cycle Model ◽  
Ice Growth

Abstract Given rapid sea ice changes in the Arctic Ocean in the context of climate warming, better constraints on the role of sea ice in CO2 cycling are needed to assess the capacity of polar oceans to buffer the rise of atmospheric CO2 concentration. Air-ice CO2 fluxes were measured continuously using automated chambers from the initial freezing of a sea ice cover until its decay during the INTERICE V experiment at the Hamburg Ship Model Basin. Cooling seawater prior to sea ice formation acted as a sink for atmospheric CO2, but as soon as the first ice crystals started to form, sea ice turned to a source of CO2, which lasted throughout the whole ice growth phase. Once ice decay was initiated by warming the atmosphere, the sea ice shifted back again to a sink of CO2. Direct measurements of outward ice-atmosphere CO2 fluxes were consistent with the depletion of dissolved inorganic carbon in the upper half of sea ice. Combining measured air-ice CO2 fluxes with the partial pressure of CO2 in sea ice, we determined strongly different gas transfer coefficients of CO2 at the air-ice interface between the growth and the decay phases (from 2.5 to 0.4 mol m−2 d−1 atm−1). A 1D sea ice carbon cycle model including gas physics and carbon biogeochemistry was used in various configurations in order to interpret the observations. All model simulations correctly predicted the sign of the air-ice flux. By contrast, the amplitude of the flux was much more variable between the different simulations. In none of the simulations was the dissolved gas pathway strong enough to explain the large fluxes during ice growth. This pathway weakness is due to an intrinsic limitation of ice-air fluxes of dissolved CO2 by the slow transport of dissolved inorganic carbon in the ice. The best means we found to explain the high air-ice carbon fluxes during ice growth is an intense yet uncertain gas bubble efflux, requiring sufficient bubble nucleation and upwards rise. We therefore call for further investigation of gas bubble nucleation and transport in sea ice.

scholarly journals A year in the life of a central California kelp forest: physical and biological insights into biogeochemical variability

2017 ◽  
Vol 14 (1) ◽  
pp. 31-44 ◽  
Author(s):  
David A. Koweek ◽  
Kerry J. Nickols ◽  
Paul R. Leary ◽  
Steve Y. Litvin ◽  
Tom W. Bell ◽  
...  
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Kelp Forest ◽  
Total Alkalinity ◽  
Kelp Forests ◽  
Saturation State ◽  
Central California ◽  
High Co2 ◽  
Spatial Gradients ◽  
Spatially Distributed

Abstract. Kelp forests are among the world's most productive marine ecosystems, yet little is known about their biogeochemistry. This study presents a 14-month time series (July 2013–August 2014) of surface and benthic dissolved inorganic carbon and total alkalinity measurements, along with accompanying hydrographic measurements, from six locations within a central California kelp forest. We present ranges and patterns of variability in carbonate chemistry, including pH (7.70–8.33), pCO2 (172–952 µatm), and the aragonite saturation state, ΩAr (0.94–3.91). Surface-to-bottom gradients in CO2 system chemistry were as large as the spatial gradients throughout the bottom of the kelp forest. Dissolved inorganic carbon variability was the main driver of the observed CO2 system variability. The majority of spatial variability in the kelp forest can be explained by advection of cold, dense high-CO2 waters into the bottom of the kelp forest, with deeper sites experiencing high-CO2 conditions more frequently. Despite the strong imprint of advection on the biogeochemical variability of the kelp forest, surface waters were undersaturated with CO2 in the spring through fall, indicative of the strong role of photosynthesis on biogeochemical variability. We emphasize the importance of spatially distributed measurements for developing a process-based understanding of kelp forest ecosystem function in a changing climate.

Calcium carbonate saturation states along the West Antarctic Peninsula

2021 ◽  
pp. 1-21
Author(s):  
Elizabeth M. Jones ◽  
Mario Hoppema ◽  
Karel Bakker ◽  
Hein J.W. de Baar
Keyword(s):  
Calcium Carbonate ◽  
Surface Water ◽  
Sea Ice ◽  
Antarctic Peninsula ◽  
Inorganic Carbon ◽  
Total Alkalinity ◽  
The West ◽  
Saturation State ◽  
West Antarctic ◽  
West Antarctic Peninsula

Abstract The waters along the West Antarctic Peninsula (WAP) have experienced warming and increased freshwater inputs from melting sea ice and glaciers in recent decades. Challenges exist in understanding the consequences of these changes on the inorganic carbon system in this ecologically important and highly productive ecosystem. Distributions of dissolved inorganic carbon (CT), total alkalinity (AT) and nutrients revealed key physical, biological and biogeochemical controls of the calcium carbonate saturation state (Ωaragonite) in different water masses across the WAP shelf during the summer. Biological production in spring and summer dominated changes in surface water Ωaragonite (ΔΩaragonite up to +1.39; ~90%) relative to underlying Winter Water. Sea-ice and glacial meltwater constituted a minor source of AT that increased surface water Ωaragonite (ΔΩaragonite up to +0.07; ~13%). Remineralization of organic matter and an influx of carbon-rich brines led to cross-shelf decreases in Ωaragonite in Winter Water and Circumpolar Deep Water. A strong biological carbon pump over the shelf created Ωaragonite oversaturation in surface waters and suppression of Ωaragonite in subsurface waters. Undersaturation of aragonite occurred at < ~1000 m. Ongoing changes along the WAP will impact the biologically driven and meltwater-driven processes that influence the vulnerability of shelf waters to calcium carbonate undersaturation in the future.

Seasonal variation in inorganic carbon parameters in the southwestern Yellow Sea

2020 ◽  
Author(s):  
Minwoo Seok ◽  
Ahra Mo ◽  
Seunghee Park ◽  
Young Ho Ko ◽  
Seongtae Yun ◽  
...  
Keyword(s):  
Yellow Sea ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Ph Sensor ◽  
Vertical Mixing ◽  
Sampling Interval ◽  
Total Alkalinity ◽  
The Yellow Sea ◽  
Sudden Increase ◽  
Saturation State

&lt;div&gt; &lt;p&gt;To better understand carbon cycles in coastal and marginal seas, time-series monitoring is essential because of large temporal variabilities. In this regard, we conducted monthly field researches from April 2017 to May 2019 at the Socheongcho (SCC) Ocean Research Site (37&amp;#176;N&amp;#8218;124&amp;#176;E) in the Yellow Sea located between Korea and China. At each survey, we collected surface seawater samples during approximately 7 days with an sampling interval of two hours (except for spring 2017). Total alkalinity (TA) and dissolved inorganic carbon (DIC) were analyzed by using VINDTA 3C system, Apollo SciTech DIC analyzer and Apollo SciTech Alkalinity Titrator. In addition, a pH sensor (SeapHOx) was installed at the surface layer from September 2018 to June 2019 which is also capable of measuring salinity, temperature and oxygen.&amp;#160;Based on the observations, we estimated a partial pressure of carbon dioxide (&lt;em&gt;p&lt;/em&gt;CO&lt;sub&gt;2&lt;/sub&gt;) and aragonite saturation state. As expected, seasonal variations in TA and DIC were strongly associated with those of salinity. We also detected a sudden increase DIC in October when vertical mixing was greatly enhanced. Despite a large outgassing during the fall season, annual mean air--sea influx of CO&lt;sub&gt;2&lt;/sub&gt; was &amp;#8764;0.61mol&amp;#183;m&lt;sup&gt;&amp;#8722;2&lt;/sup&gt;&amp;#183;year&lt;sup&gt;&amp;#8722;1&lt;/sup&gt;, suggesting that the study area was a weak sink for atmospheric CO&lt;sub&gt;2&lt;/sub&gt;. Aragonite was enerally reduced during winter (&amp;#8764;1.5). However, no undersaturation event was found during the whole investigation.&lt;/p&gt; &lt;/div&gt;

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