Subtask: Northern Gulf Coast Climate Variability

Subtask Leader: Richard Poore - USGS St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida

Aim

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

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]

Approach

Northern Gulf of Mexico Sea surface Temperature History:

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).

A SST record developed from a sediment core in the NGOM 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.

Accomplishments

• Completed study of climate variability in high-resolution sea surface temperature record covering the last 500 years in NGOM.
• Completed study of climate variability in tree-ring record from southwestern US spanning the last 2000 years.
• Completed initial microfossil analyses and dating of storm deposits in Apalachicola Bay. The results revealed the need for additional surface sediment samples to provide reference for interpreting the down core assemblages. Field work in the summer of FY 09 will obtain necessary surface (and near surface) samples to aid in the identification of storm deposits and will also obtain additional vibracores to better constrain the record of overwash deposits in Apalachicola Bay. Analyses of the new samples begun in August '09.

Publications

Manuscripts

Abstracts and Presentations

Other