Orbital Modulation of Meridional Atmospheric Heat Transport and ITCZ Variability During the Late Paleozoic Ice Age

Abstract Orbital variations redistribute seasonal insolation and can reorganize tropical rainfall, atmospheric circulation, and high‐latitude surface conditions. The energetic linkage among these processes during the late Paleozoic Ice Age remains poorly constrained. We use a 21‐member fully coupled orbital ensemble generated with the Community Earth System Model version 1.2.2 (CESM1.2.2) under late Paleozoic boundary conditions to test how eccentricity, obliquity, and perihelion phase affect hydroclimate and atmospheric energy transport. Seasonal diagnostics use a fixed‐angular calendar to compare different orbital states consistently. Eccentricity slightly increases annual mean insolation but more strongly amplifies seasonal radiative contrast. Perihelion phase sets the hemisphere of peak summer heating, and obliquity enhances high‐latitude summer energy input. These radiative controls reorganize surface temperature, precipitation, Hadley circulation, water‐vapor transport, the geometry of the Intertropical Convergence Zone, storage‐corrected atmospheric heat transport, and snow water equivalent. Tropical rain‐belt width covaries with seasonal migration, while a weak Southern Hemisphere annual mean precipitation centroid shapes the precessional response. Together, the ensemble identifies an energetically constrained pathway through which low‐latitude seasonal forcing, tropical rainfall organization, atmospheric redistribution, and cryosphere‐sensitive high‐latitude surface responses become coupled in a deep‐time icehouse climate.