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- Title
Eccentricity forcing on Tropical Ocean Seasonality.
- Authors
Beaufort, Luc; Sarr, Anta Clarisse
- Abstract
The amount of radiative energy received at the Earth's surface depends on two factors: Earth-Sun distance and sunlight angle. Because of the former factor, high eccentricity cycles can induce the appearance of seasons in the tropical ocean. In this paper, we use the Earth System model IPSL-CM5A2 to investigate the response of the low-latitude oceans to variations in Earth's orbital eccentricity. Sea Surface Temperature (SST) and Primary Production (PP) were simulated under six precession configurations at high eccentricity and two configurations with low eccentricity, representing extreme configurations observed over the past million years. Results show that high eccentricity leads to increased seasonality in SST, with an annual thermal amplitude of approximately 2.2 °C in low latitude ocean surface waters (vs. 0.5 °C at low eccentricity). PP, which already exhibits inherent seasonality under low eccentricity conditions, sees its seasonality largely increased under high eccentricity. As a consequence, we show that on long time scales the intensity of SST seasonality exhibits only the eccentricity frequency, whereas that of PP additionally follows precession dynamics. Furthermore, the seasonal variations in both SST and PP at high eccentricities are influenced by the annual placement of perihelion with its direct impact of radiative energy received in tropical regions. This leads to a gradual and consistent transition of seasons within the calendar. We introduce the concept of "eccentriseasons," referring to distinct annual thermal differences observed in tropical oceans under high eccentricity conditions, which shift gradually throughout the calendar year. These findings have implications for understanding low latitude climate phenomena such as El Niño-Southern Oscillation and monsoons in the past.
- Subjects
EL Nino; OCEAN temperature; SURFACE of the earth; RADIATION; MILANKOVITCH cycles; SEAWATER; OCEAN
- Publication
Climate of the Past Discussions, 2023, p1
- ISSN
1814-9324
- Publication type
Article
- DOI
10.5194/cp-2023-80