https://repository.kopri.re.kr/handle/201206/5540 2026-04-16T00:14:01Z https://repository.kopri.re.kr/handle/201206/7498 Title: Is Ekman pumping responsible for the seasonal variation of warm circumpolar deep water in the Amundsen Sea? Authors: Kim, Tae-Wan; Cho, Y. K.; Lee, Jae-Hak; Kim, Chang-Sin; Lee, Sang H.; Anna Wahlin; Ha, Ho Kyung Abstract: Ekman pumping induced by horizontally varying wind and sea ice drift is examined as an explanation for observed seasonal variation of the warm layer thickness of circumpolar deep water on the Amundsen Sea continental shelf. Spatial and temporal variation of the warm layer thickness in Dotson Trough was measured during two oceanographic surveys and a two-year mooring deployment. A hydrographic transect from the deep ocean, across the shelf break, and into the trough shows a local elevation of the warm layer at the shelf break. On the shelf, the water flows south-east along the trough, gradually becoming colder and fresher due to mixing with cold water masses. A mooring placed in the trough shows a thicker and warmer layer in February and March (late summer/early autumn) and thinner and colder layer in September, October and November (late winter/early spring). The amplitude of this seasonal variation is up to 60 m. In order to investigate the effects of Ekman pumping, remotely sensed wind (Antarctic Mesoscale Prediction System wind data) and sea ice velocity and concentration (EASE Polar Pathfinder) were used. From the estimated surface stress field, the Ekman transport and Ekman pumping were calculated. At the shelf break, where the warm layer is elevated, the Ekman pumping shows a seasonal variation correlating with the mooring data. Previous studies have not been able to show a correlation between observed wind and bottom temperature, but it is shown here that when sea ice drift is taken into account the Ekman pumping at the outer shelf correlates with bottom temperature in Dotson Trough. The reason why the Ekman pumping varies seasonally at the shelf break appears to be the migration of the ice edge in the expanding polynya in combination with the wind field which on average is westward south of the shelf break. 2017-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/6248 Title: Is the oceanic heat flux on the central Amundsen sea shelf caused by barotropic or baroclinic currents? Authors: KarenM.Assmann; Lee, Sang H.; Kim, Tae-Wan; Ola Kalen; Ha, Ho Kyung; AnnaK.Wahlin Abstract: The glaciers that drain the West Antarctic Ice Sheet into the Amundsen Sea are accelerating and experiencing increased basal melt of the floating ice shelves. Warm and salty deep water has been observed to flow southward in deep troughs leading from the shelf break to the inner shelf area where the glaciers terminate. It has been suggested that the melting induced by this warm water is responsible for the acceleration of the glaciers. Here we investigate the structure of the currents and the associated heat flow on the shelf using in-situ observations from 2008 to 2014 in Dotson Trough, the main channel in the western part of the Amundsen Sea shelf, together with output from a numerical model. The model is generally able to reproduce the observed velocities and temperatures in the trough, albeit with a thicker warm bottom layer. In the absence of measurements of sea surface height we define the barotropic component of the flow as the vertical average of the velocity. It is shown that the flow is dominated by warm barotropic inflows on the eastern side and colder and fresher barotropic outflows on the western side. The transport of heat appears to be primarily induced by this clockwise barotropic circulation in the trough, contrary to earlier studies emphasizing a bottom-intensified baroclinic inflow as the main contributor. 2016-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/6459 Title: Particle flux on the continental shelf in the Amundsen Sea Polynya and Western Antarctic Peninsula Authors: Hugh W. Ducklow; Patricia L. Yager; Robert M. Sherrell; Kate E. Lowry; Lee, Sang H.; Matthew Erickson; Sharon E. Stammerjohn; Anton F. Post; Stephanie E. Wilson Abstract: We report results from a yearlong, moored sediment trap in the Amundsen Sea Polynya (ASP), the first such time series in this remote and productive ecosystem. Results are compared to a long-term (1992？2013) time series from the western Antarctic Peninsula (WAP). The ASP trap was deployed from December 2010 to December 2011 at 350 m depth. We observed two brief, but high flux events, peaking at 8 and 5 mmol C m？2 d？1 in January and December 2011, respectively, with a total annual capture of 315 mmol C m？2. Both peak fluxes and annual capture exceeded the comparable WAP observations. Like the overlying phytoplankton bloom observed during the cruise in the ASP (December 2010 to January 2011), particle flux was dominated by Phaeocystis antarctica, which produced phytodetrital aggregates. Particles at the start of the bloom were highly depleted in 13C, indicating their origin in the cold, CO2-rich winter waters exposed by retreating sea ice. As the bloom progressed, microscope visualization and stable isotopic composition provided evidence for an increasing contribution by zooplankton fecal material. Incubation experiments and zooplankton observations suggested that fecal pellet production likely contributed 10？40% of the total flux during the first flux event, and could be very high during episodic krill swarms. Independent estimates of export from the surface (100 m) were about 5？10 times that captured in the trap at 350 m. Estimated bacterial respiration was sufficient to account for much of the decline in the flux between 50 and 350 m, whereas zooplankton respiration was much lower. The ASP system appears to export only a small fraction of its production deeper than 350 m within the polynya region. The export efficiency was comparable to other polar regions where phytoplankton blooms were not dominated by diatoms. 2015-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/6377 Title: Leeuwenhoekiella polynyae sp. nov., isolated from a polynya in western Antarctica Authors: Si, Ok-Ja; Rhee, Sung-Keun; Lee, Sang H.; Roh, Seong Woon; Kim, Song-Gun; Kim, Jong-Geol; Choi, Seon-Bin; Jung, Man-Young; Kim, So-Jeong Abstract: A Gram-stain-negative, motile by gliding, rod-shaped bacterial strain, designated SOJ2014-1T was isolated from surface water of a polynya in the Antarctic Ocean. A comparative 16S rRNA gene sequence analysis showed that strain SOJ2014-1T belongs to the genus Leeuwenhoekiella and is most closely related to Leeuwenhoekiella marinoflava DSM 3653T (97.5% 16S rRNA gene sequence similarity). The G+C content of the genomic DNA of strain SOJ2014-1T was 38.8 mol%. Its predominant cellular fatty acids were summed feature 3 (composed of C16 : 1v6c and/or C16 : 1v7c), iso-C17 : 0 3-OH, iso-C15 : 0, iso-C15 : 1 G and summed feature 9 (composed of iso-C17 : 1v9c and/or 10-methyl C16 : 0). DNA？DNA relatedness between strain SOJ2014-1T and close relatives, L. marinoflava DSM 3653T and Leeuwenhoekiella aequorea LMG 22550T, was below 49 %. The respiratory quinone was MK-6. The major polar lipids were phosphatidylethanolamine, an unidentified aminolipid and two unidentified lipids. The strain grew at 0？35 6C (optimum, 25 6C) with 0？14.0% (w/v) NaCl (optimum, 1.0？5.0 %). It was strictly aerobic and had different carbohydrate utilization traits compared with L. marinoflava DSM 3653T. Based on the phenotypic, chemotaxonomic and phylogenetic analyses, strain SOJ2014-1T is proposed as a representative of a novel species, Leeuwenhoekiella polynyae. The type strain is SOJ2014-1T (5KCTC 42185T5JCM 30387T). 2015-01-01T00:00:00Z