Ikaite crystals in melting sea ice - implications for pCO(2) and pH levels in Arctic surface waters

Søren Rysgaard, Ronnie N. Glud, Kunuk Lennert, M. Cooper, N. Halden, R. J. G. Leakey, F. C. Hawthorne, D. Barber

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Resumé

A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air-sea CO2 exchange. This has been complicated by the recent discoveries of ikaite (a polymorph of CaCO3 center dot 6H(2)O) in Arctic and Antarctic sea ice, which indicate that multiple chemical transformations occur in sea ice with a possible effect on CO2 and pH conditions in surface waters. Here, we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from a melting 1.7 km(2) (0.5-1m thick) drifting ice floe in the Fram Strait during summer. Our findings show that ikaite crystals are present throughout the sea ice but with larger crystals appearing in the upper ice layers. Ikaite crystals placed at elevated temperatures disintegrated into smaller crystallites and dissolved. During our field campaign in late June, melt reduced the ice floe thickness by 0.2m per week and resulted in an estimated 3.8 ppm decrease of pCO(2) in the ocean surface mixed layer. This corresponds to an air-sea CO2 uptake of 10.6 mmol m(-2) sea ice d(-1) or to 3.3 ton km(-2) ice floe week(-1). This is markedly higher than the estimated primary production within the ice floe of 0.3-1.3 mmol m(-2) sea ice d(-1). Finally, the presence of ikaite in sea ice and the dissolution of the mineral during melting of the sea ice and mixing of the melt water into the surface oceanic mixed layer accounted for half of the estimated pCO(2) uptake
OriginalsprogEngelsk
TidsskriftCryosphere
Vol/bind6
Sider (fra-til)901-908
ISSN1994-0416
DOI
StatusUdgivet - 1. aug. 2012

Citer dette

Rysgaard, S., Glud, R. N., Lennert, K., Cooper, M., Halden, N., Leakey, R. J. G., ... Barber, D. (2012). Ikaite crystals in melting sea ice - implications for pCO(2) and pH levels in Arctic surface waters. Cryosphere, 6, 901-908. https://doi.org/10.5194/tc-6-901-2012
Rysgaard, Søren ; Glud, Ronnie N. ; Lennert, Kunuk ; Cooper, M. ; Halden, N. ; Leakey, R. J. G. ; Hawthorne, F. C. ; Barber, D. / Ikaite crystals in melting sea ice - implications for pCO(2) and pH levels in Arctic surface waters. I: Cryosphere. 2012 ; Bind 6. s. 901-908.
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title = "Ikaite crystals in melting sea ice - implications for pCO(2) and pH levels in Arctic surface waters",
abstract = "A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air-sea CO2 exchange. This has been complicated by the recent discoveries of ikaite (a polymorph of CaCO3 center dot 6H(2)O) in Arctic and Antarctic sea ice, which indicate that multiple chemical transformations occur in sea ice with a possible effect on CO2 and pH conditions in surface waters. Here, we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from a melting 1.7 km(2) (0.5-1m thick) drifting ice floe in the Fram Strait during summer. Our findings show that ikaite crystals are present throughout the sea ice but with larger crystals appearing in the upper ice layers. Ikaite crystals placed at elevated temperatures disintegrated into smaller crystallites and dissolved. During our field campaign in late June, melt reduced the ice floe thickness by 0.2m per week and resulted in an estimated 3.8 ppm decrease of pCO(2) in the ocean surface mixed layer. This corresponds to an air-sea CO2 uptake of 10.6 mmol m(-2) sea ice d(-1) or to 3.3 ton km(-2) ice floe week(-1). This is markedly higher than the estimated primary production within the ice floe of 0.3-1.3 mmol m(-2) sea ice d(-1). Finally, the presence of ikaite in sea ice and the dissolution of the mineral during melting of the sea ice and mixing of the melt water into the surface oceanic mixed layer accounted for half of the estimated pCO(2) uptake",
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Rysgaard, S, Glud, RN, Lennert, K, Cooper, M, Halden, N, Leakey, RJG, Hawthorne, FC & Barber, D 2012, 'Ikaite crystals in melting sea ice - implications for pCO(2) and pH levels in Arctic surface waters', Cryosphere, bind 6, s. 901-908. https://doi.org/10.5194/tc-6-901-2012

Ikaite crystals in melting sea ice - implications for pCO(2) and pH levels in Arctic surface waters. / Rysgaard, Søren ; Glud, Ronnie N.; Lennert, Kunuk; Cooper, M.; Halden, N.; Leakey, R. J. G.; Hawthorne, F. C.; Barber, D.

I: Cryosphere, Bind 6, 01.08.2012, s. 901-908.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

TY - JOUR

T1 - Ikaite crystals in melting sea ice - implications for pCO(2) and pH levels in Arctic surface waters

AU - Rysgaard, Søren

AU - Glud, Ronnie N.

AU - Lennert, Kunuk

AU - Cooper, M.

AU - Halden, N.

AU - Leakey, R. J. G.

AU - Hawthorne, F. C.

AU - Barber, D.

PY - 2012/8/1

Y1 - 2012/8/1

N2 - A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air-sea CO2 exchange. This has been complicated by the recent discoveries of ikaite (a polymorph of CaCO3 center dot 6H(2)O) in Arctic and Antarctic sea ice, which indicate that multiple chemical transformations occur in sea ice with a possible effect on CO2 and pH conditions in surface waters. Here, we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from a melting 1.7 km(2) (0.5-1m thick) drifting ice floe in the Fram Strait during summer. Our findings show that ikaite crystals are present throughout the sea ice but with larger crystals appearing in the upper ice layers. Ikaite crystals placed at elevated temperatures disintegrated into smaller crystallites and dissolved. During our field campaign in late June, melt reduced the ice floe thickness by 0.2m per week and resulted in an estimated 3.8 ppm decrease of pCO(2) in the ocean surface mixed layer. This corresponds to an air-sea CO2 uptake of 10.6 mmol m(-2) sea ice d(-1) or to 3.3 ton km(-2) ice floe week(-1). This is markedly higher than the estimated primary production within the ice floe of 0.3-1.3 mmol m(-2) sea ice d(-1). Finally, the presence of ikaite in sea ice and the dissolution of the mineral during melting of the sea ice and mixing of the melt water into the surface oceanic mixed layer accounted for half of the estimated pCO(2) uptake

AB - A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air-sea CO2 exchange. This has been complicated by the recent discoveries of ikaite (a polymorph of CaCO3 center dot 6H(2)O) in Arctic and Antarctic sea ice, which indicate that multiple chemical transformations occur in sea ice with a possible effect on CO2 and pH conditions in surface waters. Here, we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from a melting 1.7 km(2) (0.5-1m thick) drifting ice floe in the Fram Strait during summer. Our findings show that ikaite crystals are present throughout the sea ice but with larger crystals appearing in the upper ice layers. Ikaite crystals placed at elevated temperatures disintegrated into smaller crystallites and dissolved. During our field campaign in late June, melt reduced the ice floe thickness by 0.2m per week and resulted in an estimated 3.8 ppm decrease of pCO(2) in the ocean surface mixed layer. This corresponds to an air-sea CO2 uptake of 10.6 mmol m(-2) sea ice d(-1) or to 3.3 ton km(-2) ice floe week(-1). This is markedly higher than the estimated primary production within the ice floe of 0.3-1.3 mmol m(-2) sea ice d(-1). Finally, the presence of ikaite in sea ice and the dissolution of the mineral during melting of the sea ice and mixing of the melt water into the surface oceanic mixed layer accounted for half of the estimated pCO(2) uptake

U2 - 10.5194/tc-6-901-2012

DO - 10.5194/tc-6-901-2012

M3 - Journal article

VL - 6

SP - 901

EP - 908

JO - Cryosphere

JF - Cryosphere

SN - 1994-0416

ER -