At the start of this cruise we had not expected to make it to the Alvin dive 5000 benchmark, achieved 54 years after Alvin was launched in 1964. Yet, with good weather throughout the cruise and an additional if very short dive on Thanksgiving that advanced the official dive count by one, here we are! Danik Forsman is piloting Alvin, and science observers Andreas Teske and Mandy Joye will join forces for this dive.
There are rumors to make this dive special, with interviews of the dive team while at the bottom etc. But this is a working dive – we have to deploy one long-term osmosampler that is supposed to last until February, when it will be picked up during a Guaymas visit by R/V Falkor; then there is an ambitious last-chance coring program, and animal, rock, and vent fluid collections. Of course we want to be a good dive team and systematically work through our coring program. The “collection” part of this dive takes place at the Northern Cathedral Hill site, and it turns into a spectacular surprise for everyone. Already the previous visit at this location during dive 4997 has revealed great hydrothermal scenery, but it turns out that was just a quick preview.
Here an octopus is hiding in his sponge-encrusted cave, and glowering at us and at the “Alvin 5000” sign that Danik has thoughtfully placed on his front porch. We tried to tease him to come out, but octopi are very territorial and do not leave their lair unless they have a very good reason. And anniversary photo shots do not fall into this category.
The octopus lives in the boulder field at the foot of Northern Cathedral Hill; we climb up a few meters and soon find the hydrothermal zone. The rising fluids that work their way through a hydrothermal mound emerge preferentially at the top. The entire upper hydrothermal massif with hilltops and valleys is covered in microbial mats and Riftia gardens. This one is even larger than the “Wall of Riftia” encountered during Dive 4997. It is time to reassess this spot; it is not just a peculiar northern extension of our preferred mat sampling area, Cathedral Hill. Here we have an enormous hydrothermal mound on the same order of magnitude as its more famous siblings, Rebecca’s Roost ca. 150 m to the east, and Big Pagoda, ca. 500 m to the east. Looking for a proper name – what about Trondheim, the city in Norway with the northernmost gothic cathedral ?
Alvin hovers above the Riftia gardens in search of hot water flow. Just a little over to portside we notice a column of shimmering water rising; approaching it, an extensive flange – a protruding pagoda roof of hydrothermal minerals — studded with hydrothermal chimneys floats into view. The mineral-laden fluids that escape sideways build and extend the flange; after a while the fluids are creating additional escape vents through openings in the flange, which creates this intricate display of hydrothermal chimneys. All of them are highly brittle and crumble away if even touched; the clear shimmering vent fluids here probably contain fewer metal sulfides, which build up the backbone of most chimneys. We hover at this spot for quite a while.
Finally, we remember the PR part of this dive. The chimney garden is too delicate to place the “Alvin 5000” placard, and therefore Danik dangles it into the clear hydrothermal fluid. Fortunately the plastic does not melt. The placard is not merely embellishment of this dive; it is the spear tip of a never-ending outreach campaign that most research institutions have to go through, in particular soft-money institutions like the Woods Hole Oceanographic Institution that live by research grants from the government, industry and private foundations. As a former WHOI employee, this blogger is acutely aware that research activities have to be “packaged”. Even grant-granting institutions, for example the National Science Foundation, are not immune; since they get their budget from a stingy government, the same game repeats itself on yet another level. While you are reading this blog and increase visitor traffic, you are doing a meritorious service to the entire research enterprise by demonstrating your interest – and implicitly, some degree of approval – as a tax-paying and voting citizen.
Mysterious and unfathomable nature is unconcerned with the layers of publicity that are imposed on it, and its powerful presence reminds the scientists not to forget their true vocation. So we sample the vent fluids; they turn out to be 104-105 C hot at this spot, moderate by hydrothermal standards. The niskin bottles on the Alvin basket, originally designed for cooler water, fortunately hold and we can return these samples from their source at a deep-sea hot spring at 2000 m depth to the surface, for chemical analysis.
After returning to the ship, there is indeed a photo session! Dive team and the entire science crew get photographed innumerable times for this occasion, but we reserve this spot for one picture, the Alvin team. Without them, the entire science crew would be going nowhere. From left to right, Alvin tech Drew Brewley, Alvin expedition leader Todd Litke, pilot Anthony Tarantino, Jefferson Grau and Danik Forsman, Alvin techs Nick O’Sadcia and Lane Abrams.