Seasonal decoupling of particulate organic carbon export and net primary production in relation to sea‐ice at the shelf break of the eastern Bering Sea: Implications for off‐shelf carbon export. Issue 10 (18th October 2013)

• Record Type: Journal Article
• Authors: Baumann, M. S.; Moran, S. B.; Lomas, M. W.; Kelly, R. P.; Bell, D. W.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 10(2013:Oct.)
• Page Start: 5504
• Page End: 5522
• Publication Date: 2013-10-18
• Subjects: Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/jgrc.20366
• Languages: English
• ISSNs: 2169-9275

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>[1] Particulate organic carbon (POC) export fluxes and net primary production (NPP) rates are used to assess seasonal patterns in the export ratio (<italic>e</italic>‐ratio = POC export/NPP) in relation to proximity of the sea‐ice edge near the shelf break of the eastern Bering Sea during 2008–2010. POC fluxes were relatively low in April (4.6 ± 1.6, trap, and 5.7 ± 4.3 mmol C m<sup>−2</sup> d<sup>−1</sup>, <sup>234</sup>Th‐derived) and increased in May–early June (19.9 ± 13.3 and 17.0 ± 8.8 mmol C m<sup>−2</sup> d<sup>−1</sup>). POC export reached a maximum in mid‐June–mid‐July (30.0 ± 12.6 and 48.1 ± 17.4 in 2009; 33.1 ± 27.6 and 57.0 ± 68.4 mmol C m<sup>−2</sup> d<sup>−1</sup> in 2010) and decreased by late July (13.1 ± 4.7 and 14.1 ± 8.0 mmol C m<sup>−2</sup> d<sup>−1</sup>). NPP rates were relatively high and export fluxes low near the ice‐edge in spring leading to <italic>e</italic>‐ratios <0.25. In early summer, POC export exceeded NPP at individual stations and resulted in <italic>e</italic>‐ratios >1, which is attributed to a temporal decoupling, or offset, of spring NPP and export during summer. While these observations reveal a seasonal progression in POC export and the <italic>e</italic>‐ratio, there is no direct relationship to sea‐ice proximity. Furthermore, based on a water column‐sediment <sup>234</sup>Th budget, the off‐shelf export of POC during spring‐summer is estimated to be 24 ± 35 mmol C m<sup>−2</sup> d<sup>−1</sup>, which represents an off‐shelf <italic>e</italic>‐ratio of 0.07 and 0.21 for contemporaneous seasonally averaged daily NPP and 0.17 and 0.52 for historical monthly averaged daily NPP. An implication is that off‐shelf POC transport may represent a seasonal net sink for CO<sub>2</sub> in this and other polar shelf regions.</p> </abstract>