Monday, January 11, 2016

Chasing hotspots

On board we have quite a remarkable group of scientists from different institutes of Australia, France and US (me). So, we have people from the University of Tasmania, CSIRO, the Australian National University (where I did my PhD), the University of New South Wales, the Brown University, the Curtin University, ACE CRC, IMAS, UPMC/LOMIC (France) and Scripps UCSD. We have geologists, physical oceanographers, biogeochemists, petrologists and biologists! YAY SCIENCE!!!

So, why are we going there?
The answer is in the interaction between volcanic activity and ocean. Heard and McDonald Islands are among the most active hotspot volcanoes on Earth (the others comprehend Hawai'i and Reunion Islands). Sitting roughly 4000 km far from Australia and Africa, they are basically closer to Antarctica than to any other land. They are placed on a very large plateau (Kerguelen Plateau) which is more or less 1/4 the size of all Australia! Pretty big, uh? The plateau is very old, its formation came with a huge eruption ca. 100 millions year ago (I hope I took the notes correctly today, at the seminar on board ;-) ). 

This is incredibly fascinating and during the cruise we hope to witness and video record some underwater volcanic plume, made of hot gases coming from the mantle, "some" km beneath the ocean floor..

How does this connect to the ocean, then? 
Well, magmas erupted underwater trap more of dissolved gases. And trapped amongst those elements there is iron. The presence of iron is incredibly important in the waters of the Southern Ocean… and here's why.

Bear with me for a moment: in the first 100 m of the ocean, very tiny floating plants (as small as 5 micron, called phytoplankton) live, grow and are responsible for the photosynthetic process, such as any other plant on earth. During the photosynthesis, these tiny plants, given enough light, absorb carbon dioxide and produce organic compounds (basically sugar), releasing oxygen as a waste product (that for life on Earth is fundamental). In order for a phytoplankton to do all this, it needs food (or nutrients), like us. Their nutrients come from nitrogen or silica, and, in smaller quantity, iron. When phytoplankton have all the necessary, they grow, or more specifically, they bloom. We can see these blooms using satellite images: as an example, have a look at the bloom below, which occurred in the South Atlantic Ocean (the image comes from Envisat, ESA).. how gorgeous it is! Look at the incredible structures, streams, swirls, wiggles (the white patches are clouds). These structures are due to the ocean currents, and I will talk about this later during the cruise.

The Southern Ocean is very particular in this sense, as it appears that here the growth of phytoplankton is limited by the availability of iron: this means that not everywhere in the Southern Ocean there's enough iron to allow phytoplankton to bloom. Not everywhere, correct.. but somewhere yes! 

The Kerguelen Plateau region is one of those locations in the Southern Ocean where a bloom actually occurs, and this is because, somehow, iron is present and available in the waters around the plateau! The objective of the voyage is, therefore, to search for iron deriving from underwater volcanoes activity and investigate if it causes the biological (phytoplankton) growth at the surface. In order to do this, the different teams of scientists will work non-stop to provide the first very high-resolution mapping of the sea floor around the islands, look at temperature profiles in search of deep water hot temperature (footprint of volcanic activity), record camera imaging of the water depths, run real-time numerical models in order to identify where the volcanic activity could be present and deploy instruments to collect and sample the waters in search for iron, biological activity, nutrients, etc. From satellite, the chlorophyll concentration (contained in phytoplankton) in the Kerguelen plateau region looks like the image below (MODIS 4 km resolution)

This is such an interesting location (I also based my doctoral research of 4 years on this area.. hehe!), that other 3 research voyages are heading down here, with teams from Australia, USA and Japan!


Before I close this post, I wanna give an exciting update

the last night we had our first station completed! 

All the instruments and sensors and deployments went just PERFECT! As it was the first real action moment, there was a bit of tension.. but it couldn't have gone better than that! But, even more exciting for me, 

tomorrow night (estimated local time 8:00 PM, Perth time) I will deploy the first SOCCOM float!!! 

With the help of other 2 people, the float has been secured inside, where it will patiently wait for its mission to start. It was a bit tricky to carry it there, as the waves are big today and the ship move a lot (jus have a look at the photo below: I took that one this morning from the bridge), which throws you easily out of balance. 

Ok, that's all for today's science and update from the Investigator!


"This is Major Tom to Ground Control
I'm stepping through the door
And I'm floating in a most peculiar way
And the stars look very different today
For here
Am I sitting in a tin can
Far above the world
Planet Earth is blue
And there's nothing I can do"...

Space Oddity, David Bowie (8 January 1947 – 10 January 2016)

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