THE RESPONSE OF SALT MARSHES IN THE RELICT ST. BERNARD DELTA LOBE TO TROPICAL CYCLONE ACTIVITY

From 1951 to 2009, the frequency of Atlantic tropical cyclones has gradually increased at a rate of 0.12 storms/ yr. Tropical cyclones are major drivers of geomorphic change. To identify how salt marshes from a relict Mississippi River Delta lobe responded to the past century,. five cores were collected from sites in the St. Bernard Delta complex. Three cores were taken from back-barrier salt marshes at the Chandeleur Islands and two from interior salt marshes within the delta complex. The activity of excess ²¹⁰ Pb as a function of core depth was determined to extract accretion rates for each location. Patterns in accretion rates were compared to the history of storm for the area within 125 km of the cores. The results of this study indicate that accretion rates increased in a southerly direction in cores taken from the Chandeleur Island chain from 0.07 cm/yr to 2.31 cmyr^-1. The number of samples per core ranged from 24 to 38. There is a positive correlation between an increase in accretion rates and an increase in tropical cyclones frequency for two of the three Chandeleur Islands cores and for both of the interior St. Bernard Delta cores. These findings suggest that coastal wetland dynamics are linked to tropical cyclone activities, and suggest that future changes in tropical cyclone frequency will be a major driver of salt marsh change.