- Our Research
My research interests include climate change of the past and future. I am particularly interested in how different factors influence climate change; what the past can reveal about the way climate system works, and how future climate will impact the environment and society. Specific topical interests including large scale climate response and teleconnection through ocean-atmosphere interactions, paleoclimate dynamics particular on monsoonal region and climate evolution for the past millennium.
Friedman, A.R., G.C. Hegerl, A.P. Schurer, S.-Y. Lee, W. Kong, W. Cheng, and J.C. Chiang, (2020): Forced and Unforced Decadal Behavior of the Interhemispheric SST Contrast during the Instrumental Period (1881–2012): Contextualizing the Late 1960s–Early 1970s Shift. J. Climate, 33, 3487–3509, https://doi.org/10.1175/JCLI-D-19-0102.1
Wu, C.-H., S.-Y. Lee and J. C.H. Chiang, Relative influence of precession and obliquity in the early Holocene: Topographic modulation of subtropical seasonality during the Asian summer monsoon, Quaternary Science Reviews, 191, 238-255, 2018
Chiang, J. C.H., K.S. Tokos, S.-Y. Lee and K. Matsumoto, Contrasting Impacts of the South Pacific Split Jet and the Southern Annular Mode Modulation on Southern Ocean Circulation and Biogeochemistry, Paleoceanography and Paleoclimatology, 33, 2-20, 2018
Lo, L.#, S.P. Chang, K.Y. Wei, S.Y. Lee*, T.H. Ou, Y.C. Chen, C.K. Chuang, H.S. Mii, G.S. Burr, M.T. Chen, Y.H. Tung, M.C. Tsai, D. Hodell & C.C. Shen, Nonlinear climatic sensitivity to greenhouse gases over past 4 glacial/interglacial cycles, Scientific Reports, DOI: 10.1038/s41598-017-04031-x, 2017
Lee, S.-Y., J.C.H. Chiang, and P. Chang, Tropical Pacific response to continental ice sheet topography, Climate Dynamics, 44, 2429-2446, 2015
Glacial forcing and climate response: Changes in the extent of land ice and atmospheric greenhouse gases concentrations were the major glacial forcings during the Pleistocene deglacial period. We explore the impact of glacial continental ice sheet topography on large-scale ocean-atmosphere climate in an intermediate complexity coupled model and. Other than the ice albedo effect, thickness of land ice has profound effect on climate mean state including i) a displacement of Pacific Intertropical Convergence Zone (ITCZ), ii) changes in seasonal Hadley circulation and iii) altered zonal thermo gradients. These results were also confirmed by a fully-coupled transient deglacial simulation. Analyses show that the evolution of Pacific deglacial climate with changing ice thickness has distinct quasi-linear and nonlinear parts. While the linear part is a direct response to the ice topographic changes, the nonlinear part was a result of the tropical thermocline adjustment and greenhouse forcing. This result leads us to an analysis on the correlation between mean SST and greenhouse radiative forcing. We combine a sea surface temperature records from Pacific warm pool to document a nonlinear relationship between climate sensitivity and greenhouse gas levels over the past four glacial/interglacial cycles. The sensitivity of the responses to GHG concentrations rises dramatically by a factor of 2–4 at atmospheric CO2 levels of >220 ppm.
South Pacific jet evolution and climate impact: A global atmospheric teleconnection was proposed to explain the connection between the Southern Hemisphere climate changes co-incident with North Atlantic cooling in earlier work. We argued that the climate expression and the effectiveness of teleconnection in midlatitude South Pacific might due to a modulation in the strength of the South Pacific Split Jet, a pronounced zonally-asymmetric feature of the wintertime Southern Hemisphere Westerlies. In light with the climatological similarity of seasonal Split Jet structure and wintertime Southern Annular Mode (SAM) phases, we contrast the impact of the two through simulating changes to the ocean circulation from Split Jet modulation, contrasting them against changes associated with SAM. Because the fact the both Split Jet and SAM have direct impact on ocean ventilation and implication on ocean-atmospheric CO2 source-sink fluxes, we explore the biogeochemistry effect in a biogeochemical model.