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Abstract Deep convection associated with large-scale tropical atmospheric circulations governs tropical precipitation. Under anthropogenic warming, the weakened Walker and Hadley circulations alter tropical rainfall. Ocean circulations are also expected to change due to global warming, impacting tropical atmospheric circulation systems. From the perspective of ocean heat uptake, we investigate how ocean circulation change modulates tropical atmospheric circulation and vertical motion under CO2warming by comparing fully coupled and slab-ocean simulations. We find that the slowed South Equatorial Current and subtropical cells in the Pacific induce anomalous advective warming, reducing ocean heat uptake in the central-western tropical Pacific. This, combined with increased downward radiation at the top of atmosphere and horizontal moisture advection, escalates the moisture static energy in the air column and promotes ascent in this region, shifting the Pacific Walker circulation eastward and strengthening the Pacific Hadley circulation. Across the tropical Indian Ocean, ocean heat uptake shows a dipole-like change, increasing in the eastern Indian Ocean and seas surrounding marine continents while decreasing in the western Indian Ocean. The former ocean heat uptake increase is triggered by anomalous oceanic vertical advective cooling, which abates the moisture static energy in the air column and inhibits the ascent in the area. The latter ocean heat uptake decrease is prompted by anomalous oceanic advective warming from both horizontal and vertical directions, which enhances the moisture static energy in the air column, resulting in anomalous upward motions. Over most of the tropics, ocean dynamics help attenuate the strengthening of the gross moist stability due to CO2increase, thereby promoting ascent or weakening descent in the atmosphere. Significance StatementLarge-scale tropical atmospheric circulations are expected to weaken as a result of global warming, having a significant impact on tropical precipitation. Because the atmosphere and oceans are inextricably linked, any subtle change in one can affect the other. For this reason, it is critical to understand the role of ocean circulation change in steering the response of large-scale tropical atmospheric circulation to anthropogenic warming. This study approaches the aforementioned scientific question from the novel perspective of ocean heat uptake. It demonstrates how changes in ocean circulation affect heat uptake over tropical oceans, modifying vertical motion and the Walker and Hadley cells in the tropical atmosphere in a warming climate.
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Step Increase in Eastern U.S. Precipitation Linked to Indian Ocean Warming
Abstract A step increase in annual precipitation over the eastern United States in the early 1970s commenced five decades of invigorated hydroclimate, with ongoing impacts on streamflow and water resources. Despite its far‐reaching impacts, the dynamical origin of this change is unknown. Here analyses of a century of atmospheric and oceanic data trace the dynamics to changes in the Indian Ocean. Increases in fall precipitation contribute most strongly to the step increase, and the associated mechanism is emergence of a pan‐Pacific atmospheric wave emanating from deep convection over the warming Indian Ocean. Documentation of this fall teleconnection draws attention to projected anthropogenic increases in tropical oceanic heat content and their potential impacts on hydroclimate of the midlatitudes.
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- PAR ID:
- 10444627
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 47
- Issue:
- 17
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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