An isotopic perspective on the correlation of surface ocean carbon dynamics and sea ice melting in Prydz Bay (Antarctica) during austral summer |
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| Institution: | 1. College of Ocean and Earth Sciences, Xiamen University, Xiamen 361005, China;2. State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China;1. Microbial Ecology Laboratory, Biological Oceanography Division, Dona Paula, Goa 403004, India;2. Chemcial Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa 403004, India;3. Southern Ocean Group, National Center for Antarctic Ocean Research, Sada Headland, Vasco-da-Gama, Goa, India;4. Arctic Group, National Center for Antarctic Ocean Research, Sada Headland, Vasco-da-Gama, Goa, India;1. Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido, 041-8611, Japan;2. Arctic Research Center, Hokkaido University, Kita-21 Nishi-11 Kita-ku, Sapporo, Hokkaido, 001-0021, Japan;3. Biology Department, Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA, 02543, USA;1. P.P. Shirshov Institute of Oceanology, 36, Nakhimovski Prospect, Moscow 117997, Russia;2. Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA;3. Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 1A7, Canada;4. University of Alaska Fairbanks, 505 South Chandalar Drive, Fairbanks, AK 99775, USA;1. Virginia Institute of Marine Science - College of William and Mary, United States;2. Woods Hole Oceanographic Institution, United States;1. Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow, Uttar Pradesh 226007, India;2. National Centre for Antarctic & Ocean Research, Headland Sada, Vasco-da-Gama, Goa 403804, India |
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| Abstract: | The stable carbon isotope composition of particulate organic carbon (δ13CPOC) and naturally occurring long-lived radionuclide 226Ra (T1/2=1600 a) were applied to study the variations of upper ocean (<100 m) carbon dynamics in response to sea ice melting in Prydz Bay, East Antarctica during austral summer 2006. Surface δ13CPOC values ranged from ?27.4‰ to ?19.0‰ and generally decreased from inner bay (south of 67°S) toward the Antarctic Divergence. Surface water 226Ra activity concentration ranged from 0.92 to 2.09 Bq/m3 (average 1.65±0.32 Bq/m3, n=20) and increased toward the Antarctic Divergence, probably reflecting the influence of 226Ra-depleted meltwater and upwelled 226Ra-replete deep water. The fraction of meltwater, fi, was estimated from 226Ra activity concentration and salinity using a three-component (along with Antarctic Summer Surface Water, and Prydz Bay Deep Water) mixing model. Although the fraction of meltwater is relatively minor (1.6–11.9%, average 4.1±2.7%, n=20) for the surface waters (sampled at ~6 m), a positive correlation between surface δ13CPOC and fi (δ13CPOC=0.94×fi?28.44, n=20, r2=0.66, p<0.0001) was found, implying that sea ice melting may have contributed to elevated δ13CPOC values in the inner Prydz Bay compared to the open oceanic waters. This is the first time for a relationship between δ13CPOC and meltwater fraction to be reported in polar oceans to our knowledge. We propose that sea ice melting may have affected surface ocean δ13CPOC by enhancing water column stability and providing a more favorable light environment for phytoplankton photosynthesis, resulting in drawdown of seawater CO2 availability, likely reducing the magnitude of isotope fractionation during biological carbon fixation. Our results highlight the linkage of ice melting and δ13CPOC, providing insights into understanding the carbon cycling in the highly productive Antarctic waters. |
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| Keywords: | Meltwater fraction Carbon biogeochemistry Prydz Bay Antarctica |
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