Enhanced intensity of global tropical cyclones during the mid-Pliocene warm period

Abstract

Given the threats that tropical cyclones (TC) pose to people and infrastructure, there is significant interest in how the climatology of these storms may change with climate. The global historical record has been extensively examined, but it is short and plagued with recurring questions about its homogeneity, limiting its effectiveness at assessing how TCs vary with climate. Past warm intervals provide an opportunity to quantify TC behavior in a warmer-than-present world. Here, we use a TC-resolving (∼25 km) global atmospheric model to investigate TC activity during the mid-Pliocene warm period (3.264−3.025 Ma) that shares similarities with projections of future climate. Two experiments, one driven by the reconstructed sea surface temperatures (SSTs) and the other by the SSTs from an ensemble of mid-Pliocene simulations, consistently predict enhanced global-average peak TC intensity during the mid-Pliocene coupled with longer duration, increased power dissipation, and a poleward migration of the location of peak intensity. The simulations are similar to global TC changes observed during recent global warming, as well as those of many future projections, providing a window into the potential TC activity that may be expected in a warmer world. Changes to power dissipation and TC frequency, especially in the Pacific, are sensitive to the different SST patterns, which could affect the viability of the role of TCs as a factor for maintaining a reduced zonal SST gradient during the Pliocene, as recently hypothesized.mid-Pliocene | tropical cyclone | TC-resolving climate modeling T ropical cyclones (TCs), one of the most serious natural hazards, pose significant threats to people and infrastructure in coastal regions worldwide. Both theory and modeling studies indicate that mean TC intensity and the frequency of the most intense TCs will likely increase with upward shifts in global temperatures (1-3), and there is evidence for past and projected changes in the latitude of peak TC intensity and TC hazard exposure (4, 5). Studies of how TCs respond to simulations of periods with different climate characteristics in Earth's history may complement these efforts and offer opportunities to better comprehend the processes involved through more varied external forcing.The mid-Pliocene (3.264−3.025 Ma) represents the most recent period of prolonged global warmth on a geological timescale (6). It features a continental configuration similar to present-day and higher CO 2 levels and arguably provides a potential analog to future greenhouse gas conditions. Benefiting from the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) project (7-10) and Pliocene Model Intercomparison Project (PlioMIP) (11), our knowledge on the thermal structure of the mid-Pliocene ocean is considerably improved. The latest PRISM4 reconstruction (10, 12) indicates stable temperature in the equatorial western Pacific and significant warming in the eastern part during the mid-Pliocene, whereas the PlioMIP models (13) predict higher temperatures (...

Potential impacts of enhanced tropical cyclone activity on the El Niño–Southern Oscillation and East Asian monsoon in the mid-Piacenzian warm period

“…The two experiments are designed to (i) consider the uncertainty in the estimated mid-Piacenzian TC activity (Yan et al 2016) and (ii) isolate the role of mixing over the central-eastern North Pacific, which is thought to be one of the key regions linking the extratropical and tropical ocean (Gu and Philander 1997). The other boundary conditions (e.g., topography and land cover) in the sensitivity experiments are identical to those in MP.…”

“…In addition to changes in the mean state, extreme events, such as tropical cyclones (TCs), also experienced remarkable variations in the mid-Piacenzian. Using an ultra-high resolution (~25 km) climate model, Yan et al (2016) suggested that global TCs tended to be stronger and more powerful in the mid-Piacenzian. Notably, TCs not only passively vary with climate, but also play an important role in the vertical mixing of the upper ocean and in driving oceanic poleward heat transport (Emanuel 2001).…”

“…Notably, it is argued that TC-induced vertical mixing may have contributed to the 'permanent El Niño' in the early Pliocene, hence reducing the aforementioned model-data inconsistency (Fedorov, Brierley, and Emanuel 2010). However, it remains unclear whether this might also have been the case in the mid-Piacenzian, as changes in TC activity differ greatly between the two periods, which is closely linked with the differences in the reconstructed SSTs (Fedorov, Brierley, and Emanuel 2010;Yan et al 2016). Meanwhile, TC-induced oceanic changes could in turn affect atmospheric circulations, such as the East Asian monsoon, which has not yet been examined.…”

“…Including the Pacific and North Atlantic (10°-35°N; 110°E-20°W) and South Indian Ocean and southwestern Pacific (10°-35°S; 50°E-150°W). Vertical diffusivity is not changed over the North Indian Ocean, as TC intensity and power dissipation were lower over that region in the mid-Piacenzian(Yan et al 2016).…”

Investigating Sensitivity of East Asian Monsoon to Orbital Forcing During the Late Pliocene Warm Period

“…Boreal forests expanded northward to replace tundra, and the extent of arid deserts was reduced (Salzmann et al, ). Tropical cyclone became stronger and lasted longer, with a poleward shift of the location of peak intensity (Yan et al, ). These climatic features share similarities with the projected climate in a future greenhouse world (Christensen et al, ; Haywood et al, ).…”