Hurricane-Driven Transport of Bermuda Reef Carbonate Platform Sediments to the Deep Ocean

Abstract

Tropical cyclones erode and remobilize coastal sediments but their impact on the deep ocean remains unclear. Hurricane-driven transport of carbonates and associated materials from reef carbonate platforms to the deep ocean has important implications for carbon storage, deep ecosystems and ocean chemistry as carbonate platform reef-sourced aragonite and high-Mg calcite (HMC) may dissolve and contribute to deep water total alkalinity. Here we describe two hurricane-driven resuspension events where deep sediment plumes from the Bermuda Pedestal (NW Atlantic) were advected to deep waters surrounding the Oceanic Flux Program (OFP) mooring site, ∼75 km southeast of Bermuda. Hurricanes Fabian (Cat. 3, 2003) and Igor (Cat. 1, 2010) generated large near-inertial waves propagating to >750 m depths, leading to widespread sediment resuspension from the Pedestal. Following Fabian, carbonate fluxes at the OFP site increased 15-fold, 32-fold, and 6-fold at 500, 1,500 and 3,200 m, respectively, with the 1,500 m flux equivalent to the total annual carbonate flux. OFP traps similarly captured a large detrital carbonate plume following Igor; here, the plume was shallower and persisted longer. Microscopy, geochemistry, and mineralogy confirmed that both plumes consisted of fine-grained shallow-water detrital carbonates alongside other materials accumulated on the Pedestal including phosphorus, lithogenic, authigenic, and pollutant elements. Clay-sized particles (<4 μm) in both plumes exhibited high contents of lithogenic and authigenic elements, and Zn, Cd, and V, facilitating their transport over long distances. Grain-size, elemental, and lipid composition indicated that plumes intercepted at different depths originated from different source areas on the Pedestal.