[Coral-List] Present Bleaching Event - PR & USVI etc.

scott.stripling scott.stripling at noaa.gov
Fri Sep 30 17:23:48 EDT 2005

Kristen, Alan-

To answer Kristen's question, atmospheric conditions, as well as oceanic 
conditions, must be favorable
for tropical cyclones to form. So a very warm ocean will not necessarily 
lead to tropical cyclone
development all by itself. Due to the oceanography of the local region, 
every year the upper layer
waters are warm enough to support the development of tropical cyclones 
here in the NE Caribbean.
The anomalously warm SST's that aid in setting up the biological 
conditions for bleaching can be assumed
to be connected to weaker than normal trades across or very near the 
region in question, and/or
other significant low level atmospheric changes that result in 
significant changes in oceanic currents.
Both of these conditions now appear at play in our region. Surface 
pressure across the W Atlantic and into
the northern Caribbean have generaly been below normal since the 
beginning of the year. This has helped
to produce a displaced, or much weakened "Bermuda High", with the 
dominant high pressure cell
in the Atlantic meandering closer to the Azores in the central and NE 
Atlantic. This has caused a reduced
trade wind flow across the tropical Atlantic, leading to less mixing, 
and slower regional currents. Too,
another factor at play is the larger scale horizontal circulation of the 
Atlantic. During the past 2 years, there
have been  extended periods (on the order of several weeks) with greatly 
reduced transport or flow in the
Gulf Stream off of Florida. This has to contribute to a slower than 
normal Atlantic Basin circulation and
other such anomalies in the circulation patterns.

It has been my contention that NOAA will never be able to accurately 
model the coupled global
ocean-atmosphere system unless there is a more comprehensive in situ 
oceanic observing network
established, with highest importance placed in regions of the major 
currents. In the case of the Atlantic,
the Gulf stream is the major heat input to the hemisphere, and all the 
water flowing through the Gulf stream
originates in the Caribbean. So to accurately model the entire Atlantic 
circulation, one would assume
that in situ measurements would be needed of both the input and the 
output of the Gulf stream. That
would mean monitoring the flow through the major passages into the 
Caribbean, as well as key segments
along the Gulf stream flow. So...while I am on my soap box, may I ask of 
you on the coral list, and
in NOAA to help point out this important issue to NOAA policy makers. 
One of NOAA's big
strategic goals for the next decade is monitoring and modeling of 
climate change. I argue that if
we don't have the proper input into the models, how can we accurately 
model this complex system?

Scott Stripling
NOAA-NWS San Juan 

Alan E. Strong wrote:

> Hi Kristen -- Now that would be an interesting survey....we have often 
> observed that once an overall bleaching tendency has established 
> itself over a certain region as hurricanes move though that region 
> SSTs are brought down by mixing and upwelling.  Obviously, this extra 
> "fuel" available for the tropical storm has the ability to enhance 
> these tropical storms...so much more is necessary from the atmosphere 
> to first permit a tropical depression to first develop...therein lies 
> the key....
> Right now we are witnessing a large pool of anomalously high SSTs 
> centered around the Virgin Islands...but no hurricanes have actually 
> formed or been enhance, to my knowledge, over that area yet this year...
> Cheers,
> Al
> Kristen Hoss wrote:
>> Hello,
>> I was wondering if anyone has ever studied the correlation of coral 
>> bleaching episodes as possible indicators of what hurricane activity 
>> may be like during the year?  I was wondering if there was a 
>> connection that could be used as a prediction tool, or if the 
>> correlation would just be related to the already known water 
>> temperatures and weather patterns, etc....
>> -Kristen Hoss
>> Marine Researcher
>> and Wildlife Biologist-USDA/APHIS/WS
>> */"scott.stripling" <scott.stripling at noaa.gov>/* wrote:
>>     With the NE Caribbean currently located underneath an elongated
>>     area of
>>     low pressure,
>>     light and variable winds will continue to dominate the region for 
>> the
>>     next 1 to 2 weeks.
>>     Computer models are forecasting only brief (6-12 hour periods) of
>>     anything
>>     approaching normal trade wind flow during this time. Thus the
>>     stagnant
>>     mixing conditions will
>>     persist regionally through the first week of October, at the least.
>>     Scott Stripling
>>     NOAA/NWS San Juan
>>     Alan E Strong wrote:
>>     > *NOTICE - Bleaching continues to evolve throughout Eastern
>>     Caribbean*
>>     >
>>     > Beginning in the central Keys during August (Sombrero Key
>>     especially)
>>     > the warm water episode and accompanying bleaching for this year is
>>     > progressing south and eastward through Cuba, Puerto Rico and the
>>     > Virgin Islands. This can visually be seen in our recen t 12-week
>>     > composite of HotSpot accumulations - Degree Heating Weeks (DHWs):
>>     >
>>     > http://www.osdpd.noaa.gov/PSB/EPS/SST/data2/dhwa.9.19.2005.gif
>>     >
>>     > and HotSpots:
>>     >
>>     > http://www.osdpd.noaa.gov/PSB/EPS/SST/data/hotspotwnc.gif
>>     >
>>     > Extremely high DHWs above "8" in much of the Virgin Islands are
>>     quite
>>     > worrisome as these levels in past bleaching events typically bring
>>     > some mortality to corals. This evolving episode continues to be at
>>     > near unprecedented levels of thermal stress for this region
>>     since our
>>     > satellite records began in the mid-80s. From the chart one can
>>     observe
>>     > that eastern Puerto Rico is under higher levels of thermal
>>     stress at
>>     > present than western PR....hence the recent reports of 
>> considerable
>>     > bleaching. Until some reduced solar radiation and/or wind & mixing
>>     > comes to the "rescue" we worry about prospects along much of the
>>     > Windward Islands toward South America over the next month or so.
>>     >
>>     > Sorry our repot couldn't be more positive.
>>     >
>>     > Regards,
>>     >
>>     > Al Strong
>>     > NOAA's Coral Reef Watch
>>     > http://coralreefwatch.noaa.gov/satellite/index.html
>>     >
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