Dr. Sang-Ki Lee

Oceanographer


NOAA/AOML/PHOD
4301 Rickenbacker Causeway
Miami, FL 33149, USA
Phone: (305) 361-4521
sang-ki.lee@noaa.gov


Research interests

    I am a physical oceanographer interested in a range of topics related to ocean and climate. My research aims to better understand the atmosphere-ocean processes that control the Earth's climate system, using both observations and mathematical modeling tools. Currently, my research lies in the areas of inter-ocean transports of heat, salt and carbon; El Nino diversity and its remote impact on North American climate; atmosphere-ocean processes conducive to extreme weather; and Antarctic sea-ice and ocean interactions



Research highlights

    Contrasting sea-ice trends around West Antarctica: Since late 1978, Antarctic sea-ice extent has overall expanded in all seasons in stark contrast to the retreating Arctic sea-ice extent. However, while the sea-ice extent around East Antarctica has increased monotonically, the sea-ice around West Antarctica exhibits regionally and seasonally inhomogeneous trends. For instance, Antarctic sea-ice extent in the East Pacific has decreased substantially in Austral summer. We used an ocean and sea-ice coupled model to show that the increased wind-driven upwelling of the relatively warm subsurface water, known as upper Circumpolar Deep Water, is mainly responsible for the declining sea-ice extent. This study also explains how the changes in Weddell Gyre circulations and associated meridional heat transport contributed to the increasing Antarctic sea ice in the Atlantic during Austral summer (Lee et al. 2017) [JGR editor's highlight].

    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).

    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].



Work in progress

    Dong, S., H. Lopez, S.-K. Lee, C. Meinen, G. Goni and M. Baringer, 2019: What caused the large-scale heat deficit in the South Atlantic Ocean during 2009-2012? In-review.

    Gomez, F. A., R. Wanninkhof, L. Barbero, S.-K. Lee, F. J. Hernandez Jr., 2019: Seasonal patterns of surface inorganic carbon system variables in the Gulf of Mexico inferred from a regional high-resolution ocean-biogeochemical model. Biogeosciences Discuss., https://doi.org/10.5194/bg-2019-430, In-review.

    Kim, D., S.-K. Lee, H. Lopez and M. Goes, 2019: Pacific control of the Atlantic Multidecadal Oscillation - El Nino relationship in the Community Earth System Model - Large Ensemble Simulation. In-review.

    Kim, D., S.-K. Lee and H. Lopez, 2019: Impact of the Madden-Julian Oscillation on subseasonal U.S. tornado activity and the underlying physical mechanisms. To be submitted.

    Lee, S.-K., H. Lopez, and D. Kim, A. T. Wittenberg and A. Kumar, 2019: A seasonal outlook for U.S. tornado activity based on the leading patterns of large-scale atmospheric anomalies. To be submitted.



Publications