Daily Science Report: Monday February 20th

Daily Science Report: Monday February 20th

The last sunset & the last evening at sea. We’re packed and I think the whole science party is very ready to go home. There’ll be a big party on shore tomorrow night and the team will begin flying home early on Wednesday morning. All in all it was a pretty amazing trip, Easter Island, the best mapped section of fast spread gabbroic crust underwater ever, some very exciting magnetics and the third dimension of the magnetic anomaly boundaries, and seven active hydrothermal vents, five of which have never been seen before. But soon, back to the “day-job”. The final thing is to say a big thanks to everybody, without whom none of this could have been possible; the intrepid science team, the doughty outreach team, the dauntless Jason & Sentry teams, the incredible Shipboard Science Support Group (SSSGs), and the amazing crew of the RV Atlantis, & of course the National Science Foundation (NSF).

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Daily Science Report: Friday February 19th

Daily Science Report: Friday February 19th

The first birds, packing and more report writing. Today, was the last but one day, and packing preceded apace together with that tinge of sadness that it’s nearly all over… and the real world is looming. These days, (some) internet & e-mail keeps one more in touch with the outside world during a cruise than in the good old days (no internet, limited e-mail), but we are still in our own little world out here, with three provided meals a day (the best food I’ve ever had on a research vessel) and a routine focused on the job at hand.

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Daily Science Report: Saturday February 18th

Daily Science Report: Saturday February 18th

Just over two days to go before we reach Arica, Chile and we‘re starting to be investigated by birds so we know we’re getting close to land. Today was the last of our very successful series of 2-way live broadcasts to shore led by our outreach folks Lucas Kavanagh and Theresa Williams. In total they gave 33, 45 minute sessions to 1053 people at schools, universities, and aquariums in the US, UK, and Canada! The entire science part participated in these and had a lot of fun at the same time but now it’s now lab cleaning and report writing. Sigh.

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Daily Science Report: Friday February 17th

We are on the 6th day of our 9 day transit to Arica in Chile & all is well. We just spent five days sampling, whilst maintaining orientations, on the 413 rocks we collected, with approximately half of each sample been put aside for archiving and the other half cut into smaller pieces for the science team to make thin sections, and carry out geochgemical analysis. As the rocks are going to Scripps, Jeff (Gee) and his team will take their samples for magnetic studies back at home. On another front, the good ship Jackelope is currently heading for the Pitcairn Islands!  She covered over 128km yesterday and is heading just south of west.

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Daily Science Report: Saturday February 11th

The final science day and likely my final blog. Friday evening we launched Sentry dive 428, our tenth Sentry dive, at site A. This dive was designed to complete the magnetics coverage and to illuminate a large 20km wide slump of basalts and sheeted dikes which was causing an anomalous pattern in our magnetic maps. The magnetic mapping has been a great success too producing a definitive geometry for the 3rd dimension of the magnetic stripes. We recovered sentry at 7pm and then launched the good ship Jackelope and we watched her sail off into the big Pacific. She’d been sitting in the science labs for most of the cruise, so it feels like we’ve said goodbye to an old friend. I hope she fares well & sails off to some far away exotic place. You can track her on the NOAA website.

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Staying Current

By Theresa Williams

Slackjaw Sally here with reflections on water’s wishy-washy ways.  There’s very little water movement in my part of the ocean, but being up here on the surface has me thinking about how water moves and mixes.  Tides cause the water in the ocean to slosh back and forth in its basin, winds push energy through water in the form of waves, and density stratifies water and leads to the slow creep of arctic water toward the equator along the ocean floor, but the most energetic mixing of oceanic water comes from surface currents!  

It’s all a result of the unequal heating of Earth’s surface!  Earth is roughly spherical so sunlight hits the surface at a more perpendicular angle near the equator than farther north or south.  This causes more warming near the equator.  Cooler air and water is denser and moves toward and underneath warmer air and water which is less dense.

Here’s how the water circulation gets started.  During winter at the north and south poles ocean water cools and freezes.  When water freezes, the salts remain in solution below the ice making the unfrozen ocean water saltier.  The combination of increased salinity and decreased temperature makes the water denser and it sinks.  Sinking water pushes the water beneath it toward the equator and leaves space above it for warmer water to take its place.  The warmer water cools, freezes and sinks continuing the cycle.  That cold, salty dense water moves slowly along the ocean floor until it is gradually warmed.

But there’s more going on at the surface than just water warming in the sunshine.  On the surface, there is wind caused by the uneven heating of Earth’s surface.  Air flows from areas of dense, cool, dry air (high pressure) toward areas of less dense, moist, warm air (low pressure).   Air can blow in any direction but the average direction is called the prevailing wind.  Winds transfer their energy to the water dragging the water across the ocean in increasingly deeper layers.  Due to the rotation of the planet the water doesn’t go directly in the direction of the prevailing wind; it turns to the right in the northern hemisphere and to the left in the southern hemisphere.  The water is pushed in large somewhat circular currents called gyres (rhymes with hires).  The gyres north of the equator rotate clockwise and those south of the equator rotate counterclockwise.  The South Pacific gyre moves warm water down past Australia and cool water up the west coast of South America.  There are also smaller, less prominent currents moving water around near the surface.

The ocean near the equator doesn’t experience much water movement from surface currents because warm, humid air rises there instead of generating current-driving winds.  The Atlantis is floating at about 23⁰ south of the equator on the northern edge of the South Pacific gyre.  At the end of our research in this area, we’ll launch a small sailboat, the Jackalope, with a GPS onboard to track its path around the Pacific.  The data it broadcasts to NOAA will help to improve ocean surface current maps.  Students in Laramie, Wyoming built the Jackalope as a school project to learn about the ocean currents in the Pacific Ocean.  They’ll be following Jackalope’s adventure and hoping to connect with other students on far away shores.

Catchin’ a current,

Sally

Daily Science Report: Friday February 10th

Daily Science Report: Friday February 10th

Hydrothermal vent day at Pito Seamount! We launched Jason on Thursday evening after a quick turnaround with the Jason team going above and beyond to get Jason ready for action. Just after 7pm, we were on the seafloor crossing relatively fresh lava flows- in fact the volcanic landforms were spectacular throughout the dive, which was perhaps not surprising, because Pito Seamount is more East Pacific Rise than seamount. It even has it’s own rift/axial valley. Aided by the bathymetry images and data provided by Sentry together with the expert guidance of the world renowed “ventfinder general”, and on shore scientist, Chris German, we found our first active blacksmoker vents within the first hour and spectacular they were. We named the first two Jason and Medea after the two vehicles/ROV system we are using. Jason vent was large & very “smokey” and the Medea vent was just beautiful. Later ones were named Sentry and ABE. We discovered 6 vents in total in three separate sites and 10’s of “dead” vents at various stages of decay. Most were of the “live” ones large (the tallest was 22 metres high) and delicate. Tube worms, mussels, fish, gastropods, anenomes, and crabs were common at the live vents, but Freyella like brisingid sea stars called the dead vents their home (see adjacent photo). We returned from the seafloor after lunch and later gazed at our samples of chimneys and basalt.

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Daily Science Report: Thursday February 9th

Jason dive 960 was designed to address two specific geological questions within our main gabbro area: i) Is there a continuous layer of gabbro that extends across all of our area above the troctolitic rocks? ii) detailed observation (photograpy) and sampling of the layering in the lower part of our section and additional sampling to fill in part of our area. The latter part was a little rushed as the 23.5 hour, one elevator, dive ended and Jason was recovered on deck by3:30pm. We increased our sample haul by 36 samples and passed the 400 mark for overall number of samples. Some of the samples are spectacularly complex troctolites with large dendritic/skeletal olivines and we also collected a few large samples that contain several layers. Once Jason was on board, we sped off for Pito Seamount and for our final Jason dive searching for the hydrothermal vents so effectively illuminated by the earlier sentry dive there.

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Daily Science Report: Wednesday February 8th

Success snatched from the jaws of defeat! Upon looking at the 24 samples recovered from the Jason dive which we recovered at 8am, we found 14 of the 23 samples were gabbros (we feared they were mostly sheeted dikes), and they were in a sensible stratigraphic order (despite the extensive mass wasting). Most importantly we recovered two troctolites which suggests that our main area of troctolites, 12km away, is not anomalous and that shallow primitive troctolite is a feature of fast spread oceanic crust in the area. During the middle of the day we carried out more magnetic surveying and multibeaming of the seafloor, and at 4pm, we launched Jason for yet another dive in our main gabbro area at site B to try to complete our map.

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Daily Science Report: Tuesday February 7th

Excitement spread throughout most of the ship (non-scientists included). Yesterday we sent Sentry to map the top of Pito Seamount and Sentry once again produced an incredible map of the rift valley and it’s multiple hydrothermal chimney fields. In the afternoon we launched Jason in the new area that Sentry had explored two days earlier and I slouched off to bed disappointed. Extensive sediment cover and mass wasting resulted in the dive being a rapid 1100m long transect and the dive was called to come up at 8am on wednesday.

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Daily Science Report: Monday February 6th

Jason returned at 8am with 37 more gabbro samples and a miniaturized football. Chris German even offered us a hashtag: #nomore(expletive deleted)gabbros. We are currently cutting and describing these new samples, as Sentry flys below us making another map. We also carried out another multibeam and magnetometer survey between the Jason and Sentry dives to extend our approximately 60m resolution map of the whole of Pito Deep. With only 5 more days left, changeover times are beginning to be more important in terms of maximizing on bottom time.

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Daily Science Report: Sunday February 5th

Daily Science Report: Sunday February 5th

Super Bowl day & we played touch football on the deck with Jason. Jason played quarterback and insisted on keeping the ball and we’ll see if the ball is “deflated” when it returns from the dive tomorrow. Sentry boldly went to where no folks had gone before and returned at about 2pm with another amazing bathymetry map. We were relived and excited to see outcrop which we’ll investigate with Jason later. The 1-2m resolution is truly amazing and slope instability features of all scales dominate. At the bottom of the map, we saw structures which are almost certainly rift related basaltic volcanism. Later in the day Jason descended to our main gabbro area at site to carry out detailed sampling across some key lithological boundaries- we really are trying to do field geology 4000m below the sea surface. Another 240lbs of gabbros are expected in the morning.

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