Carbon export fluxes and export efficiency in the central Arctic during the record sea‐ice minimum in 2012: a joint <sup>234sup>Th/<sup>238sup>U and <sup>210sup>Po/<sup>210sup>Pb study
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- 作者：Montserrat Roca‐Martí ; Viena Puigcorbé ; Michiel M. Rutgers van der Loeff ; Christian Katlein ; Mar Fernández‐Méndez ; Ilka Peeken ; Pere Masqué
- 刊名：Journal of Geophysical Research: Oceans
- 出版年：2016
- 出版时间：July 2016
- 年：2016
- 卷：121
- 期：7
- 页码：5030-5049
- 全文大小：3.1MB
- ISSN：2169-9291
文摘
The Arctic sea-ice extent reached a record minimum in September 2012. Sea-ice decline increases the absorption of solar energy in the Arctic Ocean, affecting primary production and the plankton community. How this will modulate the sinking of particulate organic carbon (POC) from the ocean surface remains a key question. We use the <sup>234sup>Th/<sup>238sup>U and <sup>210sup>Po/<sup>210sup>Pb radionuclide pairs to estimate the magnitude of the POC export fluxes in the upper ocean of the central Arctic in summer 2012, covering time scales from weeks to months. The <sup>234sup>Th/<sup>238sup>U proxy reveals that POC fluxes at the base of the euphotic zone were very low (2 ± 2 mmol C m<sup>−2sup> d<sup>−1sup>) in late summer. Relationships obtained between the <sup>234sup>Th export fluxes and the phytoplankton community suggest that prasinophytes contributed significantly to the downward fluxes, likely via incorporation into sea-ice algal aggregates and zooplankton-derived material. The magnitude of the depletion of <sup>210sup>Po in the upper water column over the entire study area indicates that particle export fluxes were higher before July/August than later in the season. <sup>210sup>Po fluxes and <sup>210sup>Po-derived POC fluxes correlated positively with sea-ice concentration, showing that particle sinking was greater under heavy sea-ice conditions than under partially ice-covered regions. Although the POC fluxes were low, a large fraction of primary production (>30%) was exported at the base of the euphotic zone in most of the study area during summer 2012, indicating a high export efficiency of the biological pump in the central Arctic.