I’ve published two papers recently. I’m working on a third. In the third I will use the optimization technique as detailed in the “Coral Reefs” article to predict coral bleaching under various SRES scenarios.

• van Hooidonk, R., and M. Huber (2009), Quantifying the quality of coral bleaching predictions, Coral Reefs, doi:10.1007/s00338-009-0502-z
• van Hooidonk, R., and M. Huber (2009), Equivocal evidence for a thermostat and unusually low levels of coral bleaching in the Western Pacific Warm Pool,
  Geophys. Res. Lett., 36, L06705,
  doi:10.1029/2008GL036288.

The European Coral Reef Meeting 2006 in Bremen brings together leading coral reef scientists and students to present and discuss state-of-the-art scientific results, education and outreach. I’ll be presenting a poster where I compare 3 different techniques to predict bleaching.

Next week I’ll be presenting some results at the Science Meeting (Think Tank #4) for the Integrated Coral Observing Network (ICON)/Coral Reef Early Warning System (CREWS) Project in Puerto Rico. One of the thing I want to show is a tool I made that combines databases of coral bleaching and tropical cyclone tracs. Its in a devellopping state, and currently only works for the atlantic basin, but that is going to change soon.
You can have a look here:

http://roskilde.eas.purdue.edu/~ruben/hurricanes.php

While I’m there I’ll be teaching myself video surveying techniques and I’ll establish baseline parameters oon the reef in case Puerto Rico gets hit by a tropical cyclone in the near future (not unlikely). To do the surveys we acquired a Sony DCR-HC96 mini DV camera, and a Top Dawg II underwater housing with lights and a monitor back. To help me keep the camera at a fixed distance from the substrate, two underwater lasers will be mounted on the camera housing with their beams intersecting at 50cm from the viewport. It should be interesting to dive with it, I hope I don’t scare the fish too much.

Degree heating weeks (DHW) have been calculated for 2133 reported bleaching events of different intensities. These were compared to DHW calculated for 1113 observed reefs that did not show any signs of bleaching. Both groups have a average DHW value > 0. And reefs with a higher bleaching intensity show on average higher DHW values.

To calculate bleaching thresholds NOAA uses climatology data calculated from the Multi-Channel SSTs (MCSSTs, AVHRR-based multi-channel sea surface temperatures). This climatology is based on nighttime observations from 1984-1993, with SST observations from the years 1991 and 1992 omitted. In-situ SSTs from drifting and moored buoys are used to remove any biases. To obtain the SST climatology for a specific date, the linear interpolation method is applied on the two SST monthly mean climatology files that are closest to that date, with the assumption that the SST monthly climatology is more accurate on the 15th of the month (NOAA methodology page).

I have calculated monthly mean SST by averaging daily TMI (TRMM Microwave Imager) data into monthly files for the years 1998-2005, and averaging these monthly files over the years. On average for the 24 sites observed by NOAA, TMI data results in 0.14 °C colder maximum monthly mean SST. The complete data for the 24 sites can be downloaded here.

By vertical mixing tropical cyclones can cool ambient sea temperatures. Microwave satellite data shows that tropical cyclones occur during conditions favorable to bleaching, or in locations where bleaching is actually happening. The data analysis shows that tropical cyclones can reduce the ambient sea water temperatures below maximum monthly mean, thereby ending conditions conductive to bleaching. The figure below shows TMI derived Sea Surface Temperature for the Florida Keys from August until October 2005. The red area represents temperatures above maximum monthly mean (1998-2005), temperatures where coral bleaching is likely to occur. The black vertical line represents the passing of hurricane Katrina on 26th of August. Actual bleaching has been reported in this area since the beginning of August coral-list.