Increased CO<sub>2</sub> uptake due to sea ice growth and decay in the Nordic Seas

Rysgaard, Søren; Bendtsen, Jørgen; Pedersen, Leif Toudal; Ramløv, Hans; Glud, Ronnie N.

doi:10.1029/2008jc005088

Cited by 93 publications

(153 citation statements)

References 34 publications

(53 reference statements)

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“…Hence we have added the same process as the release of salt for the other ions and dissolved gases simulated in the model (dissolved inorganic carbon (DIC), alkalinity (ALK), nutrients, dissolved organic carbon, oxygen, DI 13 C, DI 14 C). As a first approximation the surface oceanic cell is enriched in these geochemical variables in the same proportion as salt as it has been observed to be not very different on the first order (Rysgaard et al, 2007(Rysgaard et al, , 2009). The flux (F X ) of any geochemical variable X rejected during sea ice formation to the surface ocean is then:…”

Section: Implementation Of Brines In the Climber-2 Modelmentioning

confidence: 74%

“…When sea ice is formed, a flux of ions is released into the ocean as sea ice is mostly composed of fresh water (Wakatsuchi and Ono, 1983;Rysgaard et al, 2007Rysgaard et al, , 2009). Because the underlying water is then enriched in salt it becomes denser and can thus sink and transport salt to deeper waters.…”

Section: Implementation Of Brines In the Climber-2 Modelmentioning

confidence: 99%

“…around 62% of the salt flux rapidly released by sea ice formation (the first rapid salt release is ∼82% of the total salt flux rejected by sea ice formation). The impact of the brine formation on the concentration of other geochemical variables, especially dissolved inorganic carbon (DIC) has also been studied and it has been shown that DIC is rejected together with brine from growing sea ice (Rysgaard et al, 2007(Rysgaard et al, , 2009. Besides, numerical studies of this local mechanism show that the topography plays an important role in the transport of salt (Kikuchi et al, 1999).…”

Section: Implementation Of Brines In the Climber-2 Modelmentioning

confidence: 99%

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Impact of brine-induced stratification on the glacial carbon cycle

2010

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Abstract. During the cold period of the Last Glacial Maximum (LGM, about 21 000 years ago) atmospheric CO 2 was around 190 ppm, much lower than the pre-industrial concentration of 280 ppm. The causes of this substantial drop remain partially unresolved, despite intense research. Understanding the origin of reduced atmospheric CO 2 during glacial times is crucial to comprehend the evolution of the different carbon reservoirs within the Earth system (atmosphere, terrestrial biosphere and ocean). In this context, the ocean is believed to play a major role as it can store large amounts of carbon, especially in the abyss, which is a carbon reservoir that is thought to have expanded during glacial times. To create this larger reservoir, one possible mechanism is to produce very dense glacial waters, thereby stratifying the deep ocean and reducing the carbon exchange between the deep and upper ocean. The existence of such very dense waters has been inferred in the LGM deep Atlantic from sediment pore water salinity and δ 18 O inferred temperature. Based on these observations, we study the impact of a brine mechanism on the glacial carbon cycle. This mechanism relies on the formation and rapid sinking of brines, very salty water released during sea ice formation, which brings salty dense water down to the bottom of the ocean. It provides two major features: a direct link from the surface to the deep ocean along with an efficient way of setting a strong stratification. We show with the CLIMBER-2 carbon-climate model that such a brine mechanism can account for a significant decrease in atmospheric CO 2 and contribute to the glacial-interglacial change. This mechanism can be amplified by low vertical diffusion resulting from the brine-induced stratification. The modeled glacial disCorrespondence to: N. Bouttes (nathaelle.bouttes@lsce.ipsl.fr) tribution of oceanic δ 13 C as well as the deep ocean salinity are substantially improved and better agree with reconstructions from sediment cores, suggesting that such a mechanism could have played an important role during glacial times.

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Section: Implementation Of Brines In the Climber-2 Modelmentioning

confidence: 74%

Section: Implementation Of Brines In the Climber-2 Modelmentioning

confidence: 99%

Section: Implementation Of Brines In the Climber-2 Modelmentioning

confidence: 99%

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Impact of brine-induced stratification on the glacial carbon cycle

2010

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“…Marine macrophytes are often CO 2 -limited, because they have thick boundary layers that limit diffusional supply, thick tissues with high surface to volume ratio that limits uptake, and high volume density (i.e., g dry weight m −3 ) that, together with their characteristically high photosynthetic rates, lead to CO 2 depletion within the canopy (Bowes, 1989;Sand-Jensen, 1989;Hurd, 2000). CO 2 limitation of macrophyte growth may be particularly important in the Arctic because of characteristically low pCO 2 in the spring, due to depletion by ice algae and pelagic microalgae and the ice pump (Rysgaard et al, 2009), and low water temperature conducive to low diffusion rates of CO 2 in colder water as predicted by the increase in gas diffusion rate with T 3/2 by the Chapman-Enskog theory (Chapman and Cowling, 1970).…”

Section: Macrophyte-dominated Ecosystems In a Warmer Arcticmentioning

confidence: 99%

Expansion of vegetated coastal ecosystems in the future Arctic

2014

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Warming occurs particularly fast in the Arctic and exerts profound effects on arctic ecosystems. Sea ice-associated ecosystems are projected to decline but reduced arctic sea ice cover also increases the solar radiation reaching the coastal seafloors with the potential for expansion of vegetated habitats, i.e., kelp forests and seagrass meadows. These habitats support key ecosystem functions, some of which may mitigate effects of climate change. Therefore, the likely expansion of vegetated coastal habitats in the Arctic will generate new productive ecosystems, offer habitat for a number of invertebrate and vertebrate species, including provision of refugia for calcifiers from possible threats from ocean acidification, contribute to enhance CO 2 sequestration and protect the shoreline from erosion. The development of models allowing quantitative forecasts of the future of vegetated arctic ecosystems requires that key hypotheses underlying such forecasts be tested. Here we propose a set of three key testable hypotheses along with a research agenda for testing them using a broad diversity of approaches, including analyses of paleo-records, space-for-time substitutions and experimental studies. The research agenda proposed would provide a solid underpinning to guide forecasts on the spread of marine macrophytes onto the Arctic with climate change and contribute to balance our understanding of climate change impacts on the arctic ecosystem through a focus on the role of engineering species. Anticipating these changes in ecosystem structure and function is key to develop managerial strategies to maximize these ecosystem services in a future warmer Arctic.

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“…The coupling of the air-ice-ocean carbonate system has been suggested to drive a significant annual net uptake of CO 2 , through convective sequestration of CO 2 to intermediate and deeper ocean layers during wintertime sea-ice formation and subsequent CO 2 uptake from the atmosphere during springtime sea-ice melt (Rysgaard et al, 2009;Rysgaard et al, 2007). Together with seasonal biological carbon uptake within the ice (Thomas and Dieckmann, 2010;Lizotte, 2001), this outlines the basis for a seasonal carbon imbalance, which may drive CO 2 uptake from the atmosphere during springtime melting of sea ice, and mineral dissolution of trapped calcium carbonate (CaCO 3 ) within the brine channels.…”

Section: Introductionmentioning

confidence: 99%

Winter observations of CO<sub>2</sub> exchange between sea ice and the atmosphere in a coastal fjord environment

et al. 2015

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Abstract. Eddy covariance observations of CO 2 fluxes were conducted during March-April 2012 in a temporally sequential order for 8, 4 and 30 days, respectively, at three locations on fast sea ice and on newly formed polynya ice in a coastal fjord environment in northeast Greenland. CO 2 fluxes at the sites characterized by fast sea ice (ICEI and DNB) were found to increasingly reflect periods of strong outgassing in accordance with the progression of springtime warming and the occurrence of strong wind events: F ICE1 CO 2 = 1.73 ± 5 mmol m −2 day −1 and F DNB CO 2 = 8.64 ± 39.64 mmol m −2 day −1 , while CO 2 fluxes at the polynya site (POLYI) were found to generally reflect uptake F POLY1 CO 2 = −9.97 ± 19.8 mmol m −2 day −1 . Values given are the mean and standard deviation, and negative/positive values indicate uptake/outgassing, respectively. A diurnal correlation analysis supports a significant connection between site energetics and CO 2 fluxes linked to a number of possible thermally driven processes, which are thought to change the pCO 2 gradient at the snow-ice interface. The relative influence of these processes on atmospheric exchanges likely depends on the thickness of the ice. Specifically, the study indicates a predominant influence of brine volume expansion/contraction, brine dissolution/concentration and calcium carbonate formation/dissolution at sites characterized by a thick sea-ice cover, such that surface warming leads to an uptake of CO 2 and vice versa, while convective overturning within the sea-ice brines dominate at sites characterized by comparatively thin sea-ice cover, such that nighttime surface cooling leads to an uptake of CO 2 to the extent permitted by simultaneous formation of superimposed ice in the lower snow column.

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Increased CO₂ uptake due to sea ice growth and decay in the Nordic Seas

Cited by 93 publications

References 34 publications

Impact of brine-induced stratification on the glacial carbon cycle

Impact of brine-induced stratification on the glacial carbon cycle

Expansion of vegetated coastal ecosystems in the future Arctic

Winter observations of CO<sub>2</sub> exchange between sea ice and the atmosphere in a coastal fjord environment

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Increased CO2 uptake due to sea ice growth and decay in the Nordic Seas

Cited by 93 publications

References 34 publications

Impact of brine-induced stratification on the glacial carbon cycle

Impact of brine-induced stratification on the glacial carbon cycle

Expansion of vegetated coastal ecosystems in the future Arctic

Winter observations of CO&lt;sub&gt;2&lt;/sub&gt; exchange between sea ice and the atmosphere in a coastal fjord environment

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Product

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Increased CO₂ uptake due to sea ice growth and decay in the Nordic Seas

Winter observations of CO<sub>2</sub> exchange between sea ice and the atmosphere in a coastal fjord environment