Subtask 3.1: Northern Gulf Coast Climate and Ecosystem Vulnerability

Subtask Leader: Richard Poore - USGS Florida Integrated Science Center, St. Petersburg

Subtask 3.1 Aim:

Figure 3.1. Mean annual Sea Surface Temperature record developed from analyses of Mg/Ca in microfossils from a core taken from the Pigmy Basin in the northern Gulf of Mexico. Shaded bars (e.g. Sporer) below the SST curve indicate times of sunspot mimina or times of reduced solar energy output. More detailed information on the SST record can be found in Richey et al. (2007). [enlargement]

This subtask is developing and analyzing climate records for the northern Gulf Coast at decadal to century-scale resolution for the last ~ 1000 years. The records establish the timing and magnitude of climate variability in the region and help identify potential natural and human-related causes for the observed variability and change.

Studies include developing information on:

• sea surface temperature (SST) in the northern Gulf of Mexico
• flood and drought intervals impacting the northern Gulf Coast
• storm deposits in sediments from coastal lakes and estuaries
• cycles in variability

Subtask 3.1 Activities:

Northern Gulf of Mexico Sea surface Temperature History

A SST record developed from a sediment core in the northern GOM is shown in figure 3.1. mean annual SST cooled by as much as 20°C several times in the last few hundred years during an interval known as the Little Ice Age. Excursions to cooler SST coincide with reduced output of energy from the sun (sunspot minima), which indicates variation solar output may have a significant impact on earth's climate. Additional sediment cores are being studied to test and extend the results shown on figure 3.1.

Storms and Climate

Landfall of major hurricanes on the eastern and Gulf Coasts of the US appear to be related to periodic variations in the average SST of the North Atlantic Ocean known as the Atlantic Multidecadal Oscillation (AMO). The cycle of temperature variation has been identified by study of thermometer readings that extend back to the 1800's.The duration of a full AMO cycle between slightly cooler and slightly warmer average SST is on the order of 60-80 years. Work is underway to analyze variability in climate records from the Gulf Coast region to determine if an AMO-like periodicity exists back beyond the existing thermometer record.

Subtask 3.1 Publications:

Richey, J. N., Poore, R. Z., Flower, B. P., Quinn, T. M., 2007, 1400 yr multiproxy record of climate variability from the northern Gulf of Mexico, Geology, v. 35, p. 423-426.

Poore, R. Z., Quinn, T. M., Richey, Julie, and Smith, Jackie, in press, Cycles of hurricane landfalls on the east and gulf coasts of the United States linked to changes in Atlantic sea surface temperatures: Science and Storms: USGS Response to the Hurricanes of 2005, USGS Circular.

Figure 3.2. Variation in landfall of major hurricanes on the eastern United States during times of a) cold and b) warm phases of the Atlantic Multidecadal Oscillation.  Additonal discussion is in Poore et al. (in press).