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Climatic Changes During the Past 400,000 Years
Yi, HI-Il,Shin, Im-Chul Korea Association For Quaternary Research 2004 제사기학회지 Vol.18 No.2
Temperature variations, and carbon dioxide and methane concentrations are summarized during the past 400,000 years. Atmospheric temperature varied approximately within $10^{\circ}C$ during the past 400,000 years. Most of the time during the past 400,000 years, temperature was lower than today except 410000, 320000, 250000, and 125000 years ago. Temperature was slightly higher or at least similar to today during the time period of 410000. 320000, 250000, and 125000 years ago. The carbon dioxide concentration varied between 180 and 300 ppm, and the methane concentration varied between 40 and 700ppb. The present atmospheric concentration of carbon dioxide is 375 ppm and methane is 1750 ppb. Temperature was 5-$7^{\circ}C$ lower than today during the Last Glacial Maximum(18,000 years ago) and the Younger Dryas(10,000 years ago). Temprature was varied within $1^{\circ}C$ during the past 10,000 years. Especially Middle Holocene Climatic Optimum(6,000 years ago), Medieval Warm Period (500-1,000 years ago), and Little Ice Age(100-500 year ago) were global climatic events. In general, mechanism for the Middle Holocene Climatic Optimum, Medical Warm Period, and Little Ice Age can be explained by the solar insulation, however their exact mechnism is not well known. Carbon dioxide concentration during the past 400,000 years never reached the current value of 375 ppm. Furthermore, the current methane concentration never reached during the past 20Ma. However, current temperature value has happened several times during the past 400,000 years. The implication of this is unsolved question so far. This should be challenged in the near future.
Grain-Size Distribution of Source Areas of Asian Dust (Yellow Sand) in China
Yi, Hi-Il,Shin, Im-Chul Korea Association For Quaternary Research 2007 제사기학회지 Vol.21 No.2
The source regions of Asian Dusts (Yellow Sands) in the western part of China are investigated, and the soil samples are collected samples for approximately 15 days during the spring of 2005. Particle sizes of sediments are analyzed and compared with each other. These grain-size analyses from the source areas can be compared Particle sizes between loess deposits and desert sands in western part of China and desert areas show distinctive differences. Loess deposits are predominantly composed of fine sands and silts. The distinction between the final characteristics of Asian Dust particles arrived in Korea and characteristics during transportation can be recognized comparison with the Asian Dust particles collected where the dust particles settled down. The characteristics of Asian Dust particle sizes can provide the basic information regarding the transportation history from the source region.
Global and Korean Peninsula Climate Changes and Their Environmental Changes
Yi, Hi-Il,Shin, Im-Chul Korea Association For Quaternary Research 2007 제사기학회지 Vol.21 No.2
The modern foraminiferal distribution patterns and species diversity in surrounding seas of Korea are controlled by winter monsoon and characteristics of water masses. Abrupt climate change, Younger Dryas cold episode" is identified in Korea. The Younger Dryas is characterized by local extinctions of foraminifera. Several record-breaking climate phenomena observed in Korea, especially September, 2007.
The Records of Origin and Transport of Sediments From the Past to the Present in the Yellow Sea
Yi, Hi-Il,Chun, Jong-Hwa,Shin, Im-C.,Shin, Dong-Hyeok,Jou, Hyeong-Tae The Korean Society of Oceanography 2004 Journal of the Korean Society of Oceanography Vol.39 No.1
A total of 116 surface sediment samples were obtained on the Yellow Sea and analyzed for grain size and geochemical elements in order to interpret the present sediment transportation. Thirty-nine cores and 3,070 line-km shallow seismic profiles are analyzed for sedimentary records of Yellow Sea in the past. Results show that the boundary of sediment transport between Korean side and Chinese side is about between $123^{\circ}E$ and $124^{\circ}E$. The similar result is produced from Shi et al. (in this publication). Two cyclonic patterns of surface sediments are recognized in the northeastern and southwestern Yellow Sea, while the strong front zone of the mud patch and sandy sediments are found in the southeastern Yellow Sea (the southwestern part of Korean coasts). The formation of fine-particle sediment packages, called for Northwest Mudbelt Deposit (NWMD), Hucksan Mudbelt Deposit (HSMD) and Jeju Mudbelt Deposit (JJMD), are resulted from eddies (gyres) of water circulations in the Yellow Sea. NWMD has been formed by cyclonic (anticlockwise) eddy. NWMD is composed of thick, homogeneous, relatively semi-consolidated gray clay-dominated deposit. On the other hand, HSMD and JJMD are formed by anticyclonic (clockwise) eddies. They are thick, homogeneous, organic-rich gray, silt-dominated deposit. Both core and surface sediments show that the middle zone across Chinese and Korean side contains bimodal frequency of grain-size distribution, indicating that two different transport mechanisms exist. These mud packages are surrounded by sand deposits from both Korea and China seas, indicating that Yellow Sea, which is the shallow sea and epicontinental shelf, is formed mostly by sand deposits including relict sands. The seismic profiles show such as small erosional/non-depositional channels, sand-ridges and sand-waves, Pleistocene-channelfilled deposits, a series of channels in the N-S major channel system, and thick Holocene sediment package, indicating that more complex sedimentary history exists in the Yellow Sea.
이희일(Hi-Il Yi),신임철(Im Chul Shin) 한국기상학회 2010 대기 Vol.20 No.3
Impact of global warming on the ocean environment is reviewed based on most recently published publications. The most significant impact of global warming on marine environment is due to the melting of mountain and continental glaciers. Ice melting causes slow down and/or shut down of thermohaline circulation, and makes hypoxic environment for the first time, then makes anoxic with time. This can cause decreasing biodiversity, and finally makes global extinction of animals and plants. Furthermore, global warming causes sea-level rise, soil erosion and changes in calcium carbonate compensation depth (CCD). These changes also can make marine ecosystem unstable. If we emit carbon dioxide at a current rate, the global mean temperature will rise at least 6℃ at the end of this century, as predicted by IPCC (Intergovernmental Panel on Climate Change). In this case, the ocean waters become acidic and anoxic, and the thermohaline circulation will be halted, and marine ecosystems collapsed.
The Impact of Abrupt Climate Change on the Marine Ecosystem in the East Sea
Shin, Im-Chul,Yi, Hi-Il,Chung, Hyo-Sang,Kwon, Won-Tae,Chun, Jong-Hwa,Oh, Hyun-Taek Korea Association For Quaternary Research 2003 제사기학회지 Vol.17 No.2
Environmental changes caused by the abrupt climatic change are one of the important issues in the scientific community. In the East Sea, abrupt climatic shift, called Younger Dryas, is identified. The age of the Younger Dryas cold episode occurred at 11.2 ka. Overall, changes in circulation and bottom water conditions occurred during the Younger Dryas cold episode in the study area. Especially, climatic transition from meltwater spike to the Younger Dryas cold episode is characterized by significant shifts of oxygen isotope values, the coiling ratios of Neogloboquadrina pachyderma, and the planktonic foraminifers abundances. The impact of abrupt climate change on the ecosystem is very significant. In the East Sea, the calcium carbonate secreting organism(foraminifers) is replaced by silicon dioxide secreting organisms(diatom, radiolarian) after the abrupt and severe cold climatic event. Based on the Doctrine of Uniformitarianism, at least climate change for the next 100 years would be severely influence on the marine ecosystem.