My research focused on how to detect and understand changes in the ocean's geochemical and
physical processes caused by global warming, and how this can be used to better predict the global
change and impacts. Specific projects include (i) the analysis of temporal trend of dissolved oxygen
in the Southern Ocean during the past decades to detect the ocean’s response to climate change,
(ii) the development of integrated global carbon cycle model with improved parameterization of
uncertainties, and (iii) the interpretation of general circulation model results of the future climate
changes patterns due to a North Atlantic thermohaline circulation collapse.
Postdoctoral Research Associate - I worked with Dr. Mark Warner at the University of
Washington on integration and interpretation of WOCE CFC data for the Southern Ocean to
better understand the recent ventilation patterns and rates. I also carried out the basin-wide
measurement of CFCs in the East Sea (Sea of Japan) in 1999 with Mark Warner and identified
the counter-intuitive higher-oxygen and lowest-CFC content bottom water produced by dramatic
changes in deep water ventilation rates and oxygen concentrations during the past several decades.
A widely distributed CFC-maximum in intermediate water, and unexpectedly high-CFCs
in bottom water in the Yamato Basin were the additional new findings. The first CCl4 (carbon
tetrachloride) measurements carried out in the East Sea showed substantial removal in the
warmer upper waters while insignificant loss in the cold deep waters. During this period, I
collaborated with Dr. John Bullister at NOAA/PMEL and Prof. Ray Weiss at Scripps Institution
of Oceanography to elucidate the anomalous bottom-intensified CFCs in the Southern California
Borderland Basin, and to carry out a pilot groundwater tracer study in the Vashion Island, WA.
Ph.D. - I worked with Prof. Ray Weiss at SIO and, I studied large-scale ocean circulation and
ventilation using CFC tracers, and participated in several oceanographic expeditions including
WOCE. My dissertation research included the first application of the recent decreasing trend of
CFC-11/CFC-12 ratio to estimate CFC ages of ocean upper waters. Based on the CFC observation
from the WOCE/ACCE A24 expedition in the subpolar North Atlantic in 1997, I suggested that
the rapid surge of Labrador Sea Water (LSW) into the Irminger Basin might occur only during
active winter convection years and this short route is disconnected from the main circulation path
during the remaining period. In a recent collaborative study with M. Rhein (U.Bremen) and others,
we have shown the LSW distributions and calculated the formation rates (4.4-5.6 Sv) during the
late 1990s. In 1996, I measured CFCs in the East Sea during the Circulation Research of East
Asian Marginal Seas (CREAMS) program in collaborations with my Korean colleagues. It was
an exciting experience to lead the CFC program from overseeing the logistics to its successful
completion of a solo shipboard measurements. A large-scale tracer and tracer age field was
obtained in this region for the first time. I am currently developing a model to understand the
dramatic changes in deep-water ventilation rates and water properties in the East Sea during the
past several decades in context of recent climate change such as global warming and the Pacific
Decadal Oscillation. During the WOCE I3 expedition in the Indian Ocean in 1995, I have located
the first CFC trace of northward spreading Antarctic-origin bottom water in the Mascarene Basin
at 20ºS. Time-series CFC measurements of the thermocline waters off California showed that the
CFC ages have been constant over a 12-yr period even though there was a significant impact of
El Niño on the tracer burden.
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