AOML
NOAA

National Oceanic and Atmospheric Administration

Atlantic Oceanographic and Meteorological Laboratory

Physical Oceanography Division

Sang-Ki Lee (Ph.D)

Oceanographer

NOAA AOML
Physical Oceanography Division
4301 Rickenbacker Causeway
Miami, FL 33149 USA
Phone: (305) 361-4521
E-mail: sang-ki.lee@noaa.gov

Research interests

    My research interests focus on understanding the mechanisms governing global atmosphere-ocean dynamics and their impacts on climate variability. Mathematical models such as general circulation models and idealized simple models are my preferred research tools. Currently, my research lies in the areas of spring ENSO variability and associated teleconnections, inter-ocean heat transport and large-scale atmosphere-ocean processes conducive to extreme weather events.

Research highlights

    Abrupt increase in Indian Ocean heat content during the warming hiatus: Global mean surface warming has stalled since the end of the 20th century, but the net radiation imbalance at the top of the atmosphere continues to suggest an increasingly warming planet. This apparent contradiction has been reconciled by an anomalous heat flux into the Pacific Ocean, induced by a shift toward a La Nina-like state over the past decade or so. This study found that the enhanced heat uptake by the Pacific Ocean has been compensated by an increased heat transport from the Pacific Ocean to the Indian Ocean, carried by the Indonesian throughflow. As a result, Indian Ocean heat content has increased abruptly during the warming hiatus. (Lee et al. 2015) [highlighted in EOS and Nature].

    Spring persistence, transition and resurgence of El Nino: An objective method is presented to explore the differences in the space-time evolution of equatorial Pacific SST anomalies observed during El Nino events. This inter-El Nino variability is captured by two leading orthogonal modes, which explain more than 60% of the interevent variance. The first mode illustrates the extent to which warm SST anomalies in the eastern tropical Pacific persist into the boreal spring after the peak of El Nino. The second mode captures the transition and resurgence of El Nino in the following year. (Lee et al. 2014).

    What drives the southern subtropical anticyclones in austral winter?: The southern subtropical anticyclones are notably stronger in austral winter than in summer, which is in contrast with the Northern Hemisphere in which subtropical anticyclones are more intense in boreal summer consistent with the monsoon heating paradigm. Specially designed model experiments show that during boreal summer enhanced tropical convection activity in the Northern Hemisphere plays important roles in strengthening the southern subtropical anticyclones (Lee et al. 2013).

    An optimal ENSO phase for U.S. tornado outbreaks: Among the top ten extreme U.S. tornado outbreak years during 1950-2010, seven years including the top three are identified with a strongly positive Trans-Niño phase. Modeling experiments suggest that a positive Trans-Niño phase provides large-scale atmospheric conditions conducive to intense tornado outbreaks over the U.S. (Lee et al. 2013) [highlighted in Bulletin of the American Meteorological Society as Paper in Note].

    What caused the significant increase in Atlantic ocean heat content since the mid-20th century?: As the upper layer of the world ocean warms gradually during the 20th century, the inter-ocean heat transport from the Indian to Atlantic basin should be enhanced, and the Atlantic Ocean should therefore gain extra heat due to the increased upper ocean temperature of the inflow via the Agulhas leakage. Consistent with this hypothesis, instrumental records indicate that the Atlantic Ocean has warmed substantially more than any other ocean basin since the mid-20th century. A surface-forced global ocean-sea ice coupled model is used to confirm this hypothesis (Lee et al. 2011) [highlighted in Nature as Community Choice].

    Delayed advective oscillation of the AMOC: A simple dynamic model is proposed to illustrate the multidecadal oscillation of the AMOC. The proposed oscillation relies on alternating actions of positive and negative feedbacks, which are operated by a slow adjustment of the ocean circulation and the associated time delay in the advective flux response to meridional density gradient perturbation (Lee and Wang 2010).

Work in progress

    Lee, S.-K., H. Lopez, W. G. Cheon, D. Volkov, Y. Liu, and R. Wanninkhof, 2016: What caused the summer retreat and winter expansion of Antarctic sea-ice in the Amundsen and Bellingshausen Seas since 1979?, To be submitted.

Publications