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Chemical weathering and climate-a global experiment: A review
Youngsook Huh 한국지질과학협의회 2003 Geosciences Journal Vol.7 No.3
How has the Earth maintained a habitable environ-ment while its closest neighbors, Venus and Mars, are currentlytoo hot or too cold? This fortunate state has been attributed to anegative feedback hypothesis that has stood unchallenged foryears. In this model, any increase in atmospheric CO2 productionis balanced by increased CO2 uptake by silicate weathering undergreenhouse conditions. A decrease in atmospheric CO2, then, isbalanced by decreased silicate weathering rates under the colderclimate. A global experiment utilizing published geochemical datafrom large rivers at diferent latitudes helps us test the climatedependence of weathering, central to this hypothesis. When riversdraining granitic shields and basaltic provinces are compared, thereis no systematic latitudinal variation (temperature dependence) inthe rates of chemical weathering. At global scale the physicalmechanisms superimpose a threshold effect on the underlying cli-mate-dependence of silicate weathering. On tropical cratons, thebuildup of lateritic regolith suppresses weathering. In the arctic/subarctic, frost action efficiently removes the regolith and gener-ates physical exposure of silicate rocks to the weathering agents(water, CO2), thereby accelerating reaction. Available field obser-vations do not support the currently standard Clausius-Clapey-ron-Arrhenius model.
과거 해수 순환을 지시하는 해수기원 네오디뮴 동위원소 비 기록
허영숙(Youngsook Huh),장광철(Kwangchul Jang) 한국암석학회 2014 암석학회지 Vol.23 No.3
해수의 순환이 지구표면의 열 분배 및 궤도함수주기와 천년주기의 기후변화와 밀접한 관계가 있음이 알려지면서 과거 해수의 흐름을 지시할 수 있는 지시자의 개발이 관심을 끌고 있다. 이 논평에서는 해수 자 생성 네오디뮴 동위원소 비를 해수순환의 지시자로 활용하는 원리와 분석방법 그리고 두 가지 적용사례를 소개한다. 먼저 지난 빙하기-간빙기와 아빙기-아간빙기에 걸쳐 북대서양심층수 세기의 변화를 명확히 볼 수 있는 예를 소개한다. 다음으로는 북극해에서 담수의 유입과 해수순환을 재구성한 예를 보인다. Proxies for paleo-circulation are drawing much interest with the recognition that ocean circulation plays an important part in the redistribution of heat and climate change on orbital and millennial timescales. In this review, we will introduce how neodymium isotope ratios of the authigenic fraction of marine sediments can be used as a proxy for ocean circulation along with analytical methods and two case studies. The first case study shows how the North Atlantic Deep Water (NADW) has varied over the glacial-interglacial and stadial-interstadial periods. The second case study shows how the freshwater budget and water circulation within the Arctic Ocean can be reconstructed for the last glacial eriod.
Han, Yeongcheol,Huh, Youngsook Korean Society for Atmospheric Environment 2014 Asian Journal of Atmospheric Environment (AJAE) Vol.8 No.2
It is often assumed that atmospheric observations at remote sites represent long-range transport of airborne material, and local influences are overlooked. We evaluated the impact of local input on the rainwater composition at Gosan Station, a strategic site for monitoring the continental outflow from Asia. We analyzed a 14-year record of rainwater chemical composition archived by the Korea Meteorological Administration and detected local terrestrial contribution for nitrate, sulfate and ammonium. We also measured the chemical composition of rainwater sampled simultaneously at multiple locations within the premises of the Gosan Station, from which local influence with meter-scale spatial heterogeneity could be discerned. We estimate that the local input accounted for at least ~10% of the wet deposition of nitrogen and ~12% of the wet deposition of sulfur during the 14 years. This highlights the significance of the local influence, which should be carefully assessed when interpreting atmospheric observations at this site.