Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
doi:10.5194/tc-2016-166
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
15 Jul 2016
Review status
A revision of this discussion paper was accepted for the journal The Cryosphere (TC).
Impact of Icebergs on Net Primary Productivity in the Southern Ocean
Shuang-Ye Wu1,2 and Shugui Hou2 1Department of Geology, University of Dayton, Dayton, Ohio 45469, USA
2School of Geographic and Oceanic Sciences, Nanjing University, Nanjing 21009
Abstract. Productivity in the Southern Ocean (SO) is iron-limited, and supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine environment. However, recent studies show that icebergs could provide comparable amount of bioavailable iron to the SO as aeolian dust. In addition, small scale areal studies suggest increased concentrations of chlorophyll, krill, and seabirds surrounding icebergs. Based on previous research, this study aims to examine whether iceberg occurrence has a significant impact on marine productivity for the entire SO (south of 40° S), using remote sensing data of monthly iceberg amount and monthly ocean net primary productivity (NPP) covering the period 2002–2014. Using global and geographically weighted multiple linear regression models, and controlling for temperature, our analyses show that iceberg presence has a small, yet statistically significant, positive impact on the SO NPP. NPP in the SO is largely influenced by temperature, which could explain 43 % of the total variance in NPP with the standardized coefficient of 0.68. However, in places with iceberg presence, temperature influence weakens, indicated by lower partial temperature R2 (0.19) and standardized coefficient (0.45). Meanwhile, iceberg probability could independently explain 2 % of the NPP variance with a standardized coefficient of 0.15. Although small, this influence is statistically significant at 0.01 level. The geographically weighted regression model reveals spatial variation of these relationships. The results suggest that as iceberg quantity increases, their positive influence on NPP also increases, as indicated by increasing iceberg partial R2 and standardized coefficient in the models.

Citation: Wu, S.-Y. and Hou, S.: Impact of Icebergs on Net Primary Productivity in the Southern Ocean, The Cryosphere Discuss., doi:10.5194/tc-2016-166, in review, 2016.
Shuang-Ye Wu and Shugui Hou
Shuang-Ye Wu and Shugui Hou
Shuang-Ye Wu and Shugui Hou

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Short summary
The primary productivity in the Southern Ocean (SO) is limited by the amount of iron available for biological activities. Recent studies show that icebergs could be a main source of iron to the SO. Based on remote sensing data, our study shows that iceberg presence has a small, yet statistically significant, positive impact on productivity. As iceberg quantity increases, their positive influence on productivity also increases. This impact could serve as a negative feedback to the climate system.
The primary productivity in the Southern Ocean (SO) is limited by the amount of iron available...
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