• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.291-299
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• 2006

The observed ocean barotropic circulation is not completely explained by the classical wind-driven circulation theory. Although it is believed that the thermohaline forcing plays a role in the ocean barotropic circulation to some degree, how much the thermohaline forcing contributes to the barotropic circulation is not well known. The role of thermohaline circulation driven by changes in temperature and salinity in the Southern Ocean (SO) water masses on the Antarctic Circumpolar Current (ACC) transport is investigated using a coupled ocean - atmosphere - sea ice - land surface climate system model in a Last Glacial Maximum (LGM) context. Withthe implementation of glacial boundary conditions in a coupled model, a substantial increase in the ACC transport by about 75% in 80 years of integration and 25% in the near LGM equilibrium is obtained despite of the decreases in the magnitude of wind stresses over the SO by 33% in the transient time and 20% in the near-equilibrium. This result suggests that the increase in the barotropic ACC transport is due to factors other than the wind forcing. The change in ocean thermohaline circulation in the SO seems to play a significant role in enhancing the ACC transport in association with the change in the bottom pressure torque.

• Proceedings of KOSOMES biannual meeting
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• 2017.04a
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• pp.41-41
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• 2017

• Ocean and Polar Research
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• v.21 no.2
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• pp.127-136
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• 1999

Radiolarian assemblages from KODOS area were analyzed in order to understand the biostratigraphy and paleoceanography of deep-sea sediment from the Northeast Equatorial Pacific. The sediment core was divided into two or three units on the basis of the chemical and physical properties. In the upper sediment, mixtures of Quaternary and Tertiary radiolarians are found indicating active reworking processes. Dissolution of radiolarians seem to increase with depth. Radiolarians are seldom in Unit III presumably due to dissolution and corrosion. The middle part of unit I appears to correspond to Collosphaera invaginata Zone (0.21 Ma). Unit II belongs to Collosphaera tuberosa Zone. Based on the absence of Stylatractus universus, we estimate its age to be younger than 0.42 Ma. Based on our analyses of radiolarians in Unit I and II, we estimated the age of unit III as Tertiary, particularly from Oligocene to Miocene. There may to be hiatuses of more than 3 My from late Miocene to Pliocene, which probably resulted from erosion and dissolution by the Antarctic Bottom Water Sedimentation rates during Quaternary range from 0.15 to 0.50 mm/ky with significant variabilities among stations. Radiolarians in the study area were mostly warm-water species.

• Ocean and Polar Research
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• v.23 no.2
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• pp.77-95
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• 2001

Temperature, salinity, nutrients, chlorophyll-a, and primary production were measured within the upper 200 m water column in the area around the South Shetland Islands in January, 2000. Surface temperature was relatively high in the Drake Passage north of the South Shetland Islands and low in the northeastern area of the Antarctic Peninsula. In contrast, surface salinity was low in the Drake Passage and increased toward the Antarctic Peninsula, reaching the maximum value in the northeastern area of the Antarctic Peninsula. Surface nutrients were low in the Drake Passage and high in the area near the South Shetland Islands. Surface chlorophyll-a was also low in the Drake Passage and near the Antarctic Peninsula and high in the area of the northern King George Island. The study area could be classified as four geographical zones based on the characteristic shape of the T/S diagrams;the Drake Passage, the Bransfield Strait, the mixed zone, and the Weddell Sea. Each geographical zone showed apparently different physical, chemical, and biological characteristics. Phytoplankton biomass was relatively low in the Drake Passage and the Weddell Sea and high in the Bransfield Strait and the mixed zone. The low phytoplankton biomass in the Weddell Sea could be explained by the low water temperature and deep surface mixing down to 200 m. The high grazing pressure and low availability of iron could be responsible for the low phytoplankton biomass in the Drake Passage.

• Korean Journal of Remote Sensing
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• v.34 no.6_2
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• pp.1203-1213
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• 2018

In Arctic and Antarctic ocean, remote sensing is the most effective observation for environmental changes due to the inaccessibility of the regions. Even though satellite, UAV (Unmanned Aerial Vehical) are well known remote sensing platforms, and research vessel also used for automatic measurement on the regions, varied environment of Polar regions require time series and wide coverage of data. Especially, in high latitude, apply an optical satellite remote sensing is not easy due to low sun altitude. In this paper, we introduce an operation of hyper-spectrometer (HyperSAS/Satlantic inc.) which is mounted on Ice Breaker Research Vessel ARAON of Korea Polar Research Institute since 2010, to acquire an above water reflectance atomatically through every research cruise on Arctic and Antarctic ocean and transit both regions. In addition to, auxiliary data for the remotely acquired data, in situ water sampling were also obtained. The above water reflectance and in situ water sampling data are continuously acquired since 2010 will contribute to improve an Ocean Color algorithm in the high latitude and help to understand ocean reflectances over from high latitude through low latitude. Preliminary result from above water reflectance showed characteristics of Arctic ocean and Antarctic Ocean and used to develop algorithms for estimating various ocean factors such as chlorophyll and suspended sediment.

• ALGAE
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• v.24 no.3
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• pp.139-147
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• 2009

Microalgae using a submersible fluorescence probe in water column (up to 100 m) were measured during the austral summer of 2006 (February) in Prydz Bay, East Antarctica (triangular-shaped embayment in the Indian sector of Southern Ocean). Concurrently, environmental parameters such as temperature, salinity and nitrogen (nitrate, ammonium, urea) uptake rates were measured. The concentration of phytoplankton is relatively high due to availability of high nutrients and low sea surface temperature. Phytoplankton community is dominated by diatoms whereas cryptophytes are in low concentration. The maximum concentration of total chlorophyll is 14.87 ${\mu}g\;L^{-1}$ and is attributed to upwelled subsurface winter water due to local wind forcing, availability of micro-nutrients and increased attenuation of photosynthetically available radiation (PAR). Concentration of blue-green algae is low compared to that of green algae because of low temperature. Comparatively high concentration of yellow substances is due to the influence of Antarctic melt-water whereas cryptophytes are low due to high salinity and mixed water column. Varied concentrations of phytoplankton at different times of Fluoroprobe measurements suggest that the coastal waters of Prydz Bay are influenced by changing sub-surface water temperature and salinity due to subsurface upwelling induced by local winds as also melting/freezing processes in late summer. The productivity is high in coastal water due to the input of macro as well as micro-nutrients.

• Ocean and Polar Research
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• v.24 no.3
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• pp.267-278
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• 2002

This study investigated the spatial characteristics of warming trends and the dipole-like pattern of temperature field in the Antarctic Peninsula using surface air temperature (SAT) of 10 stations in the vicinity of the Antarctic Peninsula. SAT data for the 1962-2001 period at 6 stations (Rothera, Faraday/Vernadsky, Bellingshausen, Orcadas, Esperanza, Halley) revealed in general the larger warming trends in autumn and winter except for Halley. The largest warming was shown for August in the west side of the Peninsula (more than $0.9^{\circ}C/decade$). On the other hand, the recent 14-year SAT data showed the strong warming trends at 9 stations except for Halley in the earlier period (April-June) than August for the 1962-2001 period. The largest warming appeared in May at Esperanza and Butler Island. SAT of the two sides showed significant positive correlations over most of the period except for the mid- and the late 1970s, in which significant negative correlations were found. In the correlation analysis between SAT and sea surface temperature (SST) anomalies in the NINO 3.4 region, strong negative correlation was found in the west side of the Peninsula. Details of the correlation analysis exhibited that the negative correlation was significantly strong from the early 1980s to the mid-1990s. However, it was difficult to find significant correlations of ENSO with SAT in the east side of the Peninsula. So, in this study it failed to find out clearly the out-of-phase relationship of SAT across the Antarctic Peninsula.

• Ocean and Polar Research
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• v.44 no.1
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• pp.83-97
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• 2022

The Amundsen Sea in West Antarctica is one of the most affected regions by climate change, but it is one of the least studied realms due to difficulties in access. Korea Polar Research Institute (KOPRI) launched a research project in the Amundsen Sea in 2010 using the icebreaker research vessel (IBRV) Araon and has been conducting various research initiatives. In this paper, previous researches derived from the Amundsen Sea Embayment by Korean researchers are introduced. Through previous studies, researchers have been able to interpret the environmental and biogeochemical changes according to the inflow Circumpolar Deep Water (CDW) and provide information for climate models. In particular, researches using radiocarbon isotopes (¹⁴C) were introduced to understand the physical and biogeochemical mechanisms of the carbon cycle in the Amundsen Sea. Opportunely, with the construction of a second icebreaker research vessel, the direction for systematic and long-term polar data acquisition can be presented.

• Journal of the Korean earth science society
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• v.23 no.5
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• pp.442-453
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• 2002

A total of 64 species belonging to 23 genera of diatom fossils are identified from the Core GC 98-06 in the southern Drake Passage, Antarctica. The diatom assemblages are dominated by Actinocyclus actinochilus, Coscinodiscus asteromphalus, Eucampia antarctica, Fragilariopsis kerguelensis, Thalassiosira lentiginosa, T. ritscheri and T. anguste-lineata, which are about 73% of the assemblage. Open water species are more abundant than sea ice species in the diatom assemblages of the core. Fragilariopsis. kerguelensis and Thalassiosira lentiginosa are valuable indicators of the habitats. Especially, F. kerguelensis represent the influence of waters from the Antarctic Circumpolar Current. Sea ice taxa represents the influence of cold waters from Bransfield Strait Water and melt water from the sea-ice at during warm periods. The reworked diatoms such as Denticulopsis dimopha (Miocene) and D. hustedtii (Pliocene) are occurred with Quaternary species (Actinocyclus actinochilus, Fragilariopsis kerguelensis, Thalassiosira lentiginosa, and T. glacilis). The presence of reworked diatoms indicates the transportation of the older diatoms into the Drake passage from the circumference sediments, due to strong bottom current activity of Antarctic circumpolar deep water.

• Ocean and Polar Research
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• v.45 no.3
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• pp.141-153
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• 2023

Biological pump processes generated by diatom production in the surface water of the Southern Ocean play an important role in exchanging CO₂ gas between the atmosphere and ocean. In this study, the biogenic opal content of the sediments was measured to elucidate the variation in the primary production of diatoms in the surface water of the Southern Ocean since the last glacial period. A piston core (COR-1bPC) was collected from the Conrad Rise, which is located in the Indian sector of the Southern Ocean. The sediments were mainly composed of siliceous ooze, and sediment lightness increased and magnetic susceptibility decreased in an upward direction. The biogenic opal content was low (38.9%) during the last glacial period and high (73.4%) during the Holocene, showing a similar variation to that of Antarctic ice core ΔT and CO₂ concentration. In addition, the variation of biogenic opal content in core COR-1bPC is consistent with previous results reported in the Antarctic Zone, south of the Antarctic Polar Front, in the Southern Ocean. The glacial-interglacial biogenic opal production was influenced by the extent of sea ice coverage and degree of water column stability. During the last glacial period, the diatom production was reduced due to the penetration of light being limited in the euphotic zone by the extended sea ice coverage caused by the lowered seawater temperature. In addition, the formation of a strong thermocline in more extensive areas of sea ice coverage led to stronger water column stability, resulting in reduced diatom production due to the reduction in the supply of nutrient-rich subsurface water caused by a decrease in upwelling intensity. Under such environmental circumstances, diatom productivity decreased in the Antarctic Zone during the last glacial period, but the biogenic opal content increased rapidly under warming conditions with the onset of deglaciation.