Regional shifts in paleohurricane activity over the past 1500 years reconstructed from blue hole sediment records in the Bahama Archipelago

Abstract:

With rising sea levels and projected increases in the frequency of intense tropical cyclones, coastal communities are becoming more vulnerable to hurricane-induced flooding. Unfortunately, our knowledge of the climate influence on hurricane variability is limited. With only the 170 years of biased observations, we cannot (i) rigorously identify the climate dynamics that generate amplified storm activity on longer timescales or (ii) elucidate hurricane-climate interactions during a mean climate which differs substantially from today. Here, we present a transect of cores collected from a blue hole off Middle Caicos in the Turks & Caicos Islands. Storm deposits found across cores in the transect record the passage of hurricanes of varying intensity passing to the south of Middle Caicos over the past 1500 years including Hurricane Kate in 1985 and Hurricane Irma in 2017. The record indicates multi-decadal periods of elevated storm strikes on the island. Combining this new record with three other published records from The Bahamas, we present the first compilation of annually-resolved paleohurricane records from blue holes on the Bahama Archipelago. The compilation includes work from Abaco, South Andros, and Long Island in The Bahamas. We find that the storms recorded by these four sites capture 80% of the variance in a set of downscaled storms (≥ tropical storm strength) passing through the Bahama Archipelago. By creating new compilations of published records from New England and northwest Florida, we assess regional-scale shifts in North Atlantic hurricane activity on multi-decadal timescales. Taken together, these compilations indicate a basin-wide increase in activity during the Medieval Climate Anomaly (900-1100 CE). Afterwards (1100 CE to present), there are century-scale periods with more storms in the Bahama Archipelago and New England coinciding with less storm activity in Florida. We argue our observations reflect a shift from straight-moving storms impacting the U.S. Gulf Coast to recurving storms impacting the U.S. East Coast over the past millennium. This could be a result of changes in hurricane tracks related to variations in the North Atlantic Subtropical High and/or changes in local environmental conditions (i.e., sea surface temperature, vertical wind shear).