Detrital Zircon Data Support Stronger, Inland‐Tracking Hurricanes During the Miocene Climatic Optimum, Maryland USA

Abstract Climate models run under warmer‐than‐modern conditions indicate that hurricanes pass closer to the US East Coast and show that a higher proportion of tropical cyclones achieve “major hurricane” strength with winds >209 km/hr. Empirical observations indicate that the dominant southward longshore current direction off the US East Coast is reversed during passage of tropical cyclones and that the duration of the reversal is longer with cyclones that pass closer to the coast. Inland or coast‐proximal hurricane tracks place the strongest northward‐directed winds over the shallow marine shelf resulting in northward longshore currents, with velocities sufficient to move zircon grains in inner‐shelf marine waters. We use these observations to hypothesize that detrital zircon sediment provenance in warmer‐than‐modern conditions would be dominated by southern Appalachian and Piedmont sources. We test this hypothesis by conducting U‐Pb analysis of detrital zircons from Miocene through modern samples from the Chesapeake Bay area (Calvert Cliffs, Maryland), midway between Newfoundland and Georgia. Modeling of the detrital zircon data using non‐negative matrix factorization yields endmembers that are similar to potential empirical sources spanning the coastline from Newfoundland to Georgia. Forward linear mixing with those empirical sources shows that there is a shift from southern‐dominated sources during the Miocene Climatic Optimum (MCO) to northern‐dominated sources during the Middle Miocene Climatic Transition. The same northern sources dominate modern beach samples. We conclude that the sediment provenance data support the hypothesis that there is a greater proportion of stronger hurricanes and that they pass closer to the coastline during warmer‐than‐modern climates.