Large, non-Redfieldian drawdown of nutrients and carbon in the extratropical North Atlantic Ocean (46°N): Evidence for dinitrogen fixation?

Geun Ha Park, Kitack Lee, Rik Wanninkhof, Jia Zhong Zhang, Dennis A Hansell, Richard A. Feely

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Considerable drawdown of total dissolved inorganic carbon (CT) and oversaturation of oxygen (O2) within a cold (∼15°C) oligotrophic eddy in the extratropical North Atlantic Ocean (46°N, 20.5°W) indicate that, despite the absence of nitrate (NO3 -), the eddy was highly productive. Estimates of net community production using the mass balances of CT and O2 were two to five times greater than those obtained using the mass balance of NO 3 -. The remineralization rates obtained using the integrated rates of CT and NO3 - accumulation and O2 utilization for the upper thermocline waters (35-300-m depth) were in agreement with CT- and O2-based net community production over the same period; however, all the estimates exceeded the NO 3 --based net community production by a factor of two to five, pointing to a considerable accumulation of NO3 - in the upper thermocline in excess of changes in the mixed-layer NO 3 - inventory. The amount of this excess NO 3 - suggests that a considerable fraction of the net community production was not supported by the mixed-layer NO3 - inventory and that an external source of NO3 - must be present. Of the various mechanisms that might explain the inequity between NO3 - drawdown in the surface layer and NO 3 - accumulation in the upper thermocline, N2 fixation is the most viable yet surprising mechanism for producing such excess NO3 - in this oligotrophic eddy. A significant fraction of net community production in oligotrophic extratropical waters could be supported by processes that are not fully explored or to date have been considered to be insignificant.

Original languageEnglish (US)
Pages (from-to)1697-1704
Number of pages8
JournalLimnology and Oceanography
Volume53
Issue number5
StatePublished - Sep 2008

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drawdown
thermocline
Atlantic Ocean
nitrogen fixation
fixation
eddy
mixed layer
carbon
nutrient
mass balance
nutrients
remineralization
nitrates
dissolved inorganic carbon
oxygen
surface layer
nitrate
water
North Atlantic Ocean
rate

ASJC Scopus subject areas

  • Oceanography
  • Aquatic Science

Cite this

Large, non-Redfieldian drawdown of nutrients and carbon in the extratropical North Atlantic Ocean (46°N) : Evidence for dinitrogen fixation? / Park, Geun Ha; Lee, Kitack; Wanninkhof, Rik; Zhang, Jia Zhong; Hansell, Dennis A; Feely, Richard A.

In: Limnology and Oceanography, Vol. 53, No. 5, 09.2008, p. 1697-1704.

Research output: Contribution to journalArticle

Park, Geun Ha ; Lee, Kitack ; Wanninkhof, Rik ; Zhang, Jia Zhong ; Hansell, Dennis A ; Feely, Richard A. / Large, non-Redfieldian drawdown of nutrients and carbon in the extratropical North Atlantic Ocean (46°N) : Evidence for dinitrogen fixation?. In: Limnology and Oceanography. 2008 ; Vol. 53, No. 5. pp. 1697-1704.
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abstract = "Considerable drawdown of total dissolved inorganic carbon (CT) and oversaturation of oxygen (O2) within a cold (∼15°C) oligotrophic eddy in the extratropical North Atlantic Ocean (46°N, 20.5°W) indicate that, despite the absence of nitrate (NO3 -), the eddy was highly productive. Estimates of net community production using the mass balances of CT and O2 were two to five times greater than those obtained using the mass balance of NO 3 -. The remineralization rates obtained using the integrated rates of CT and NO3 - accumulation and O2 utilization for the upper thermocline waters (35-300-m depth) were in agreement with CT- and O2-based net community production over the same period; however, all the estimates exceeded the NO 3 --based net community production by a factor of two to five, pointing to a considerable accumulation of NO3 - in the upper thermocline in excess of changes in the mixed-layer NO 3 - inventory. The amount of this excess NO 3 - suggests that a considerable fraction of the net community production was not supported by the mixed-layer NO3 - inventory and that an external source of NO3 - must be present. Of the various mechanisms that might explain the inequity between NO3 - drawdown in the surface layer and NO 3 - accumulation in the upper thermocline, N2 fixation is the most viable yet surprising mechanism for producing such excess NO3 - in this oligotrophic eddy. A significant fraction of net community production in oligotrophic extratropical waters could be supported by processes that are not fully explored or to date have been considered to be insignificant.",
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