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Abstract The Intertropical Convergence Zone (ITCZ) has an annual mean location north of the equator today. The factors determining this location and the evolution to its modern state are actively debated. Here we investigate how the Atlantic Meridional Overturning Circulation (AMOC) influences the ITCZ during the early‐to‐middle Miocene. By conducting a sensitivity study with an open Canadian Arctic Archipelago gateway, we show that North Atlantic Deep‐Water formation strengthens the AMOC, in alignment with Miocene North Atlantic ventilation proxies. A vigorous AMOC increases northward Atlantic Ocean heat transport and cross‐equatorial atmospheric energy transport shifts southwards to compensate, pushing the ITCZ northwards. Our study supports AMOC development as a strong contributor to the ITCZ's northern location today. Existing proxy‐based interpretations of ITCZ history are too sparse to strongly confirm these results. We predict a strong in‐phase relationship between AMOC strength and ITCZ's northward location, which should be testable in high resolution paleoclimate records.
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A Multivariate Probabilistic Framework for Tracking the Intertropical Convergence Zone: Analysis of Recent Climatology and Past Trends
Abstract Due to its importance for water availability in the tropics and subtropics, efficient tracking of the seasonal and long‐term shifts of the intertropical convergence zone (ITCZ) is of great value. Current approaches, which are based on tracking changes in the annual mean of single variables, ignore the intra‐annual dynamics, while more sophisticated methods are computationally intensive. Here we propose a new probabilistic framework to track the ITCZ, which is based on tracking the location of maximum precipitation and minimum outgoing longwave radiation in overlapping longitudinal windows. Our framework is seasonally and longitudinally explicit, allows for joint consideration of multiple variables to define the ITCZ, and is flexible in its implementation, thus, it can be used in analyses of different scales and scopes. We apply our framework to analyze the recent climatology of the ITCZ and report a southward trend in its location over central Pacific in the late twentieth century.
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- PAR ID:
- 10374763
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 45
- Issue:
- 23
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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While the zonal-mean position of the intertropical convergence zone (ITCZ) is well explained using the zonal-mean energetic framework, the regional variations of the ITCZ have been more difficult to characterize. We show a simple metric, the interhemispheric tropical sea surface temperature (SST) contrast, is useful for estimating the local ITCZ position over seasonal and interannual timescales in modern observations. We demonstrate a linear correspondence between the SST contrast and ITCZ position across oceanic sectors. Though consistently linear, the sensitivity of the ITCZ position to the SST contrast varies from ~1°/K to ~7°/K depending on location. We also find that the location of the Western Pacific interannual ITCZ is negatively correlated with the temperature of the North Atlantic Ocean. This result may help put constraints on past and future regional migrations of the ITCZ.more » « less
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