Cho
Kyoung-Ho
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Kyoung-Ho
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ArticleN2O dynamics in the western Arctic Ocean during the summer of 2017(Nature Research, 2021-06-15) Heo, Jang-Mu ; Kim, Seong-Su ; Kang, Sung-Ho ; Yang, Eun Jin ; Park, Ki-Tae ; Jung, Jinyoung ; Cho, Kyoung-Ho ; Kim, Ju-Hyoung ; Macdonald, Alison M. ; Yoon, Joo-Eun ; Kim, Hyo-Ryeon ; Eom, Sang-Min ; Lim, Jae-Hyun ; Kim, Il-NamThe western Arctic Ocean (WAO) has experienced increased heat transport into the region, sea-ice reduction, and changes to the WAO nitrous oxide (N2O) cycles from greenhouse gases. We investigated WAO N2O dynamics through an intensive and precise N2O survey during the open-water season of summer 2017. The effects of physical processes (i.e., solubility and advection) were dominant in both the surface (0–50 m) and deep layers (200–2200 m) of the northern Chukchi Sea with an under-saturation of N2O. By contrast, both the surface layer (0–50 m) of the southern Chukchi Sea and the intermediate (50–200 m) layer of the northern Chukchi Sea were significantly influenced by biogeochemically derived N2O production (i.e., through nitrification), with N2O over-saturation. During summer 2017, the southern region acted as a source of atmospheric N2O (mean: + 2.3 ± 2.7 μmol N2O m−2 day−1), whereas the northern region acted as a sink (mean − 1.3 ± 1.5 μmol N2O m−2 day−1). If Arctic environmental changes continue to accelerate and consequently drive the productivity of the Arctic Ocean, the WAO may become a N2O “hot spot”, and therefore, a key region requiring continued observations to both understand N2O dynamics and possibly predict their future changes.
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ArticleAnalysis of the Beaufort Gyre freshwater content in 2003-2018(American Geophysical Union, 2019-12-11) Proshutinsky, Andrey ; Krishfield, Richard A. ; Toole, John M. ; Timmermans, Mary-Louise ; Williams, William J. ; Zimmermann, Sarah ; Yamamoto-Kawai, Michiyo ; Armitage, Thomas ; Dukhovskoy, Dmitry S. ; Golubeva, Elena ; Manucharyan, Georgy E. ; Platov, Gennady A. ; Watanabe, Eiji ; Kikuchi, Takashi ; Nishino, Shigeto ; Itoh, Motoyo ; Kang, Sung-Ho ; Cho, Kyoung-Ho ; Tateyama, Kazutaka ; Zhao, JingHydrographic data collected from research cruises, bottom‐anchored moorings, drifting Ice‐Tethered Profilers, and satellite altimetry in the Beaufort Gyre region of the Arctic Ocean document an increase of more than 6,400 km3 of liquid freshwater content from 2003 to 2018: a 40% growth relative to the climatology of the 1970s. This fresh water accumulation is shown to result from persistent anticyclonic atmospheric wind forcing (1997–2018) accompanied by sea ice melt, a wind‐forced redirection of Mackenzie River discharge from predominantly eastward to westward flow, and a contribution of low salinity waters of Pacific Ocean origin via Bering Strait. Despite significant uncertainties in the different observations, this study has demonstrated the synergistic value of having multiple diverse datasets to obtain a more comprehensive understanding of Beaufort Gyre freshwater content variability. For example, Beaufort Gyre Observational System (BGOS) surveys clearly show the interannual increase in freshwater content, but without satellite or Ice‐Tethered Profiler measurements, it is not possible to resolve the seasonal cycle of freshwater content, which in fact is larger than the year‐to‐year variability, or the more subtle interannual variations.
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ArticleThe Pacific water flow branches in the eastern Chukchi Sea(Elsevier, 2023-11-10) Pickart, Robert S. ; Lin, Peigen ; Bahr, Frank B. ; McRaven, Leah T. ; Huang, Jie ; Pacini, Astrid ; Arrigo, Kevin Robert ; Ashjian, Carin J. ; Berchok, Catherine L. ; Baumgartner, Mark F. ; Cho, Kyoungho ; Cooper, Lee W. ; Danielson, Seth L. ; Dasher, Doug H. ; Fuiwara, Amane ; Gann, Jeanette C. ; Grebmeier, Jacqueline M. ; He, Jiangfeng ; Hirawake, Toru ; Itoh, Motoyo ; Juranek, Laurie ; Kikuchi, Takashi ; Moore, G. W. Kent ; Napp, Jeffrey M. ; John Nelson, R. ; Nishino, Shigeto ; Statscewich, Hank ; Stabeno, Phyllis J. ; Stafford, Kathleen M. ; Ueno, Hiromichi ; Vagle, Svein ; Weingartner, Thomas J. ; Williams, Bill ; Zimmermann, Sarah L.The flow of Pacific-origin water across the Chukchi Sea shelf impacts the regional ecosystem in profound ways, yet the two current branches on the eastern shelf that carry the water from Bering Strait to Barrow Canyon – the Alaskan Coastal Current (ACC) and Central Channel (CC) Branch – have not been clearly distinguished or quantified. In this study we use an extensive collection of repeat hydrographic sections occupied at three locations on the Chukchi shelf, together with data from a climatology of shipboard velocity data, to accomplish this. The data were collected predominantly between 2010 and 2020 during the warm months of the year as part of the Distributed Biological Observatory and Arctic Observing Network. The mean sections show that mass is balanced for both currents at the three locations: Bering Strait, Point Hope, and Barrow Canyon. The overall mean ACC transport is 0.34 ± 0.04 Sv, and that of the CC Branch is 0.86 ± 0.11 Sv. The dominant hydrographic variability at Bering Strait is seasonal, but this becomes less evident to the north. At Barrow Canyon, the dominant hydrographic signal is associated with year-to-year variations in sea-ice melt. Farther south there is pronounced mesoscale variability: an empirical orthogonal function analysis at Bering Strait and Point Hope reveals a distinct ACC mode and CC Branch mode in hydrography and baroclinic transport, where the former is wind-driven. Finally, the northward evolution in properties of the two currents is investigated. The poleward increase in salinity of the ACC can be explained by lateral mixing alone, but solar heating together with wind mixing play a large role in the temperature evolution. This same atmospheric forcing also impacts the northward evolution of the CC Branch.