Simulation of oxygen isotopes and circulation in a late Carboniferous epicontinental sea with implications for proxy records

Reconstructions of ancient ocean chemistry are largely based on geochemical proxies obtained from epicontinental seas. Mounting evidence suggests that these shallow inland seas were chemically distinct the nearby open ocean, decoupling records broader conditions. Here we use isotope-enabled Community Earth System Model to evaluate extent which oxygen isotopic composition late Carboniferous sea, North American Midcontinent Sea (NAMS), reflects its open-ocean sources and connect isotope variability in sea large-scale ocean-atmosphere processes. results support estuarine-like circulation patterns demonstrated by past empirical studies suggest orographic runoff produced decreases surface seawater δ18O (δ18Ow) up ∼3‰ between NAMS bordering ocean. Simulated temperatures relatively constant across broadly reproduced proxy-based paleotemperatures for model-based values δ18Ow used, indicating offshore-onshore proxy is primarily influenced freshening. bottom water also biogenic calcite using δ18Ow, suggesting benthic marine fossil freshening coastal upwelling. In addition, glacial-interglacial variations nearshore counteract effects temperature values, salinity should be considered δ18O-based estimates glacioeustatic level change regions NAMS. Our emphasize importance constraining dynamics interpretations as paleotemperature, salinity, glacioeustasy.