• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.4
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• pp.225-233
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• 2001

In order to find out the role of sea-ice in the climate system, a thermodynamic sea-ice model has been developed and included in the ocean general circulation model, MOM2, for the construction of OGCM/sea-ice coupled model in this study. By using the model developed, seasonal mean sea-ice distribution has been simulated, first of all. The role of sea-ice in the sense of large scale ocean circulation has been studied by comparing the results of OGCM/sea-ice coupled model experiment with OGCM-standalone experiment. At the same time, the coupled model has been verified by comparing and analysing the results of the other models and observation. The coupled model has reasonably simulated the overall seasonal distribution of sea-ice in the high latitudes of both hemispheres. In the comparative analysis between the OGCM/sea-ice coupled and OGCM-standalone experiments, the sea-ice is playing important roles on maintaining not only the distributions of temperature and salinity in high latitudes of both hemispheres, but also the meridional ocean circulation associated with south ocean cell, southern hemisphere cell and zonal ocean circulation such as a circum-polar current.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.2
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• pp.210-226
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• 2013

Ever since the Arctic region has opened its mysterious passage to mankind, continuous attempts to take advantage of its fastest route across the region has been made. The Arctic region is still covered by thick ice and thus finding a feasible navigating route is essential for an economical voyage. To find the optimal route, it is necessary to establish an efficient transit model that enables us to simulate every possible route in advance. In this work, an enhanced algorithm to determine the optimal route in the Arctic region is introduced. A transit model based on the simulated sea ice and environmental data numerically modeled in the Arctic is developed. By integrating the simulated data into a transit model, further applications such as route simulation, cost estimation or hindcast can be easily performed. An interactive simulation system that determines the optimal Arctic route using the transit model is developed. The simulation of optimal routes is carried out and the validity of the results is discussed.

• 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.

• Journal of the Korean earth science society
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• v.28 no.5
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• pp.545-555
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• 2007

Ocean general circulation model developed by GFDL on the basis of MOM4 of FMS are examined and evaluated in order to elucidate the global ocean status. The model employs a tripolar grid system to resolve the Arctic Ocean without polar filtering. The meridional resolution gradually increases from $1/3^{\circ}$ at the equator to $1^{\circ}$ at $30^{\circ}N(S)$. Other horizontal grids have the constant $1^{\circ}$ and vertical grids with 50 levels. The ocean is also coupled to the GFDL sea ice model. It considers tidal effects along with fresh water and chlorophyll concentration. This model is integrated for a 100 year duration with 96 cpu forced by German OMIP and CORE dataset. Levitus, WOA01 climatology, serial CTD observations, WOCE and Argo data are all used for model validation. General features of the world ocean circulation are well simulated except for the western boundary and coastal region where strong advection or fresh water flux are dominant. However, we can find that information concerning chlorophyll and sea ice, newly applied to MOM4 as surface boundary condition, can be used to reduce a model bias near the equatorial and North Pacific ocean.

• Ocean and Polar Research
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• v.32 no.4
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• pp.379-386
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• 2010

This study examines changes in the Arctic sea ice associated with global warming by analyzing the climate coupled general circulation models (CGCMs) provided in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. We selected nine models for better performance under 20th century climate conditions based on two different criteria, and then estimated the changes in sea ice extent under global warming conditions. Under projected 21st century climate conditions, all models, with the exception of the GISS-AOM model, project a reduction in sea ice extent in all seasons. The mean reduction in summer (-63%) is almost four times larger than that in winter (-16%), resulting an enhancement of seasonal variations in sea ice extent. The difference between the models, however, becomes larger under the 21st century climate conditions than under 20th century conditions, thus limiting the reliability of sea-ice projections derived from the current CGCMs.

• Proceedings of the Korean Quaternary Association Conference
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• 2004.11a
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• pp.37-43
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• 2004

The response of the CCCma coupled climate model to the imposition of LGM conditions is investigated. The global mean SAT and SST decrease by about $10^{\circ}C$ and $5.6^{\circ}C$ in the coupled model. Tropical SST decreases by $6.5^{\circ}C$, whereas CLIMAP reconstructions suggest that the tropics cool by only about $1.7^{\circ}C$, although the larger tropical cooling is consistent with the more recent proxy estimates. With the incorporation of a full ocean component, the coupled model gives a realistic spatial SST pattern, capturing features associated with ocean dynamics that are seen in the CLIMAP reconstructions. The larger decrease of the surface temperature in the model is associated with a reduction in global precipitation rate (about 15%). The tropical Pacific warm pool retreats to the west and a mean La $Ni\tilde{n}a$-like response is simulated with less precipitation over the central Pacific and more in the western tropical Pacific. The more arid ocean climate in the LGM results in an increase in SSS almost everywhere. This is particularly the case in the Arctic Ocean where large SSS increase is due to a decrease in river discharge to the Arctic Ocean associated with the accumulation of snow over the ice sheet, but in the North Atlantic by contrast SSS decreases markedly. This remarkable reduction of SSS in the North Atlantic is attributed to an increase in fresh water supply by an increase in discharges from the Mississippi and Amazon rivers and an increase in P-E over the North Atlantic ocean itself. The discharges increase in association with the wetter LGM climate south of the Laurentide ice sheet and in South America. The fresh water capping of the northern North Atlantic results in a marked reduction of deep convection and consequently a marked weakening of the North Atlantic overturning circulation. In the LGM, the maximum overturning stream function associated with the NADW formation decreases by about 60% relative to the control run, while in the Southern Ocean, oceanic convection is stronger in the LGM due to reduced stratification associated with an increase in SSS and a decrease in SST and the overturning stream function associated with the formation of AABW and the outflow increases substantially.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.1
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• pp.16-24
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• 1998

In this study, Ocean General Circulation Model (OGCM) has been developed as a counterpart of Atmospheric General Circulation (AGCM) for the study of coupled ocean-atmosphere climate system. The oceanic responses to given atmospheric boundary conditions have been investigated using the OGCM. In an integration carried out over 100 simulated years with climatological monthly mean data (EXP 1), most parts of the model reached a quasi-equilibrium climate reproducing many of the observed large-scale oceanic features remarkably well. Some observed narrow currents, however, such as North Equatorial Counter Current, were inevitably distorted due to the model's relatively coarse resolution. The seasonal changes in sea ice cover over the southern oceans around Antarctica were also simulated. In an experiment (EXP 2) under boundary condition of 10-year monthly data (1982-1991) from NCEP/NCAR Reanalysis Project model properly reproduced major oceanic changes during the period, including El Ni$\tilde{n}$os of 1982-1983 and 1986-87. During the ENSO periods, the experiment showed eastward expansion of warm surface waters and a negative vertical velocity anomalies along' the equator in response to expansion of westerly current velocity anomalies as westerly wind anomalies propagated eastward. Simulated anomalous distribution and the time behavior in response to El Ni$\tilde{n}$o events is consistent with that of the observations. These experiments showed that the model has an ability to reproduce major mean and anomalous oceanic features and can be effectively used for the study of ocean-atmosphere coupling system.

• Korean Journal of Agricultural and Forest Meteorology
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• v.12 no.1
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• pp.11-22
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• 2010

According to IPCC 4th Assessment Report, concentration of carbon dioxide has been increasing by 30% since Industrial Revolution. Most of IPCC $CO_2$ emission scenarios estimate that the concentration will reach up to double of its present level within 100-year if the current tendency continues. The global warming has resulted in the agro-climate change over the Korean Peninsula as well. Accordingly, it is necessary to understand the future agro-climate induced by the increase of greenhouse gases in terms of the agro-climatic indices in the Korean peninsula. In this study, the future climate is simulated by an atmosphere/ocean/land surface/sea ice coupled general circulation climate model, Pusan National University Coupled General Circulation Model(hereafter, PNU CGCM), and by a regional weather prediction model, Weather Research and Forecasting Model(hereafter, WRF) for the purpose of a dynamical downscaling. The changes of the vegetable period and the crop growth period, defined as the total number of days of a year exceeding daily mean temperature of 5 and 10, respectively, have been analyzed. Our results estimate that the beginning date of vegetable and crop growth periods get earlier by 3.7 and 17 days, respectively, in spring under the $CO_2$-doubled climate. In most of the Korean peninsula, the predicted frost days in spring decrease by 10 days. Climatic production index (CPI), which closely represent the productivity of rice, tends to increase in the double $CO_2$ climate. Thus, it is suggested that the future $CO_2$ doubled climate might be favorable for crops due to the decrease of frost days in spring, and increased temperature and insolation during the heading date as we expect from the increased CPI.