CLIVARmageddon!

9 September 2013

20^o 30'

28^o 42'

Rough weather ahead!

For those plotting our cruise track, especially along the East Coast, you may have noticed that you can follow our travels using the free chart provided by your local newspaper every year around July or August. Of course, I'm referring to a hurricane tracking chart, and we are expecting to experience some inclement weather over the next couple of days. Tropical storm Humberto (which means "famous giant" ... no kidding) has developed quickly and surprisingly close to the coast of Africa, and you can compare its projected storm path with our own location here:

shiptracker.noaa.gov/shiptracker.html

Select the "Ronald H. Brown" from the "Pick a Ship" drop-down box on the right, and it should plot our progress and current location. You can also select the "Weather" option on the map, which should show Humberto's current location and projected cruise track.

As you can see, we're on a direct course towards the storm, but never fear ... the captain, chief scientist and NOAA have decided that if Humberto continues to develop rapidly in our direction, we will head due east towards Africa, allowing Humberto to pass behind us to our west. Once the storm has passed, we'll return to our cruise line and continue our science operations.

Storm path of Tropical Inconvenience Humberto

Speaking of, why would we ever risk a scientific expedition right in the middle of hurricane season? Well, the same winds which carry these seasonal tropical storms from Africa across the Atlantic also carry something else: Saharan dust.

Much of the ocean's surface waters have low concentrations of iron, which is an essential micronutrient for many microscopic marine plants (also known as phytoplankton; see Rachel's August 7th post below). Saharan dust is rich in iron, and the supply of this dust to the ocean could fuel the phytoplankton to grow. These dust storms can be so intense that they extend across the Atlantic, over Florida and the Gulf of Mexico, even reaching Texas:
http://blog.chron.com/weather/2013/08/its-august-where-the-heck-are-the-hurricanes/

http://blog.chron.com/weather/2013/08/from-africa-with-love-dust-invades-texas/

As part of the trace metal team from Pacific Marine Environmental Laboratory/University of Washington and Florida State University, we are collecting samples to help us to estimate the iron supply to the ocean by these dust storms. We are collecting aerosol samples (dry deposition) and rain samples (wet deposition) as well as ocean water samples for dissolved and particulate iron. With these four pieces of the puzzle, we hope to build a more complete picture of the cycling of iron and other trace metals in the ocean.



Iron-rich dust is blown over the ocean, fueling the growth of phytoplankton,
which form the base of the food chain in the ocean. (image by Jack Cook, Woods Hole
Oceanographic Institution).
For more info, see www.whoi.edu/page.do?pid=10095&tid=282&cid=11126

Other useful links:
2007 article about trace metal sampling during the CLIVAR cruises
http://www.livescience.com/2077-desert-dust-feeds-world-oceans.html

Negative effects of iron supply in the Gulf of Mexico
http://earthobservatory.nasa.gov/Newsroom/view.php?id=21884