Sally meets the Sentry team
Just the other day I was chatting with fellow sailor, and marine technician, Stephen Jalickee and he mentioned that he had been following and chatting with a remarkable person who was very close by…. so I decided to follow up…
Yesterday we crossed the path of Jeanne Socrates on the sailing vessel Nereida. We were about 100 miles west of her and experiencing the end of the storm system she mentioned in her blog the day before.
Jeanne is a 76-year-old British yachtswoman who holds the record as the oldest woman to circumnavigate the world solo and unassisted and is the only woman to circumnavigate solo from North America. She was awarded the Cruising Club of America’s Blue Water Medal in 2013. Currently, she is attempting to become the oldest person to circumnavigate the world solo and unassisted. That record is held by a Japanese man, Minoru Saito who was 71 years old when he accomplished it.
Jeanne expects to be at sea for 7 to 8 months nonstop and plans to get back to her starting point without any outside help or the use of her motor. The motor is sealed so it will be obvious if she uses it. If she manages this without setting foot on land or using the boat's engine, she will hold the record for the oldest person to sail solo around the world, non-stop and unassisted.
After leaving British Columbia October 3, 2018, Jeanne successfully navigated around Cape Horn in December. She sailed past our current location two days ago. The photo below is from her blog.
Sailing septuagenarians! Go Jeanne!
I’ve been hearing a lot about the Roaring Forties and how rough the sea could be in our study area between 38 and 42 degrees south of the equator. What are the Roaring Forties? I asked a friend I met off the port bow, Ali the albatross. Ali spends her time soaring on air currents, so she’s practically an expert.
Here’s how I understand what she told me. We all know that the sun’s energy heats Earth’s surface unevenly. We also know that temperature differences cause density differences and density differences cause wind when less dense, warm air rises and more dense, cool air sinks. What’s interesting is how so much wind ends up at latitudes south of 40 degrees south.
In the southern hemisphere warm air rises at the equator and moves south while cold air moves north to replace it. Our atmosphere is too thin to carry the warm air high up for very far, so it sinks back toward the surface at around 30 degrees south. From there it travels along Earth’s surface southward to about 60 degrees where it rises above Antarctica. So, you’ve got this surface air moving southward between 30 and 60 degrees south, but that’s not all that’s happening because the Earth is rotating on its axis as well.
The Earth is roughly spherical, so different parts of the planet are moving at different speeds. The equator has a circumference of about 40,000 km, so it’s moving at about 1,700 km per hour. At 40 degrees south, Earth’s circumference is smaller and it’s traveling at about 1,300 km per hour. The speed of a point on the surface of the planet just gets slower the farther south you go. As air moves over the surface, the surface is slowing down dramatically and that makes the air’s movement relative to the surface much faster! Voila – high speed winds!
Of course, the winds aren’t always in exactly the same place or moving at the same speeds – there’s a lot going on down here. A big factor is the seasons. During southern summer, the area of the planet receiving the most sunlight is shifted toward the south pole and so is the area of highest wind. Likewise, during winter the sun energy is shifted away from the south pole and so is the area of highest wind. That’s a simplified version, but that’s how I understand it.
Roaring Forties sounds rough, but if you go ten degrees farther south, you’ll reach the Furious Fifties and another ten degrees will get you to the Screaming Sixties! I’m happy to avoid those extreme wind speeds!
I bet you’re wondering why you don’t hear about these outrageous wind speeds in the northern hemisphere. Well, it’s because there’s so much more land up there to break up the air masses that the wind just can’t get up a good head of steam. Down here, there’s only Tasmania, a slip of southern Australia and the south end of South America in the 40’s and only that tip of South America in the 50’s. The wind runs unhindered in the south!
All this excitement’s got me winded!
Last night we were treated to a beautiful bioluminescent show off the stern of the ship. Standing on the fantail, we watched glowing blobs emerge from beneath the ship as we sailed over the water. This light show was likely the result of sailing through a dinoflagellate algal bloom. Under certain conditions, dinoflagellates bloom in dense layers at the ocean surface. The ocean looks reddish-brown in daylight and has a sparkly sheen at night as the algae move in the waves. The shoreline picture below shows what we saw in the wake of the ship. Since we were out in the deep ocean, the only light we saw was from the bioluminescent organisms and the stars. Wow! It was pretty!
Bioluminescent organisms live everywhere in the ocean – from surface to seafloor and coast to open ocean. They are very common in the deep ocean where sunlight only penetrates the top of the water. Since the ocean covers more than 70% of Earth and can be miles deep in some places, I’d say that bioluminescence is the most common form of communication on the planet!
Bacteria, algae, jellyfish, worms, crustaceans, sea stars, fish, sharks, squid, and many other types of organisms use chemical reactions to produce light energy within their bodies. The critical molecule is luciferin and it reacts with oxygen to produce light. Creatures control when they light up through their body chemistry and nervous system. Calcium ions in the body usually start the reaction when there is a physical disturbance (response to attack) or when the animal is trying to attract a mate or a meal.
I have bioluminescence too! and I mostly use mine for hunting. I have red patches below my eyes that produce a red light to let me see short distances around me. Red is invisible to most creatures down here because red wavelengths don’t travel far in water. I can see red – I’m special that way – and I use my red light to scope out tasty organisms to snack on. I also have green patches on my cheeks. I produce green light with them to trick fish into coming close thinking they’ll get a snack. Mwahaha! When they get close, I snap them up in my huge jaws and swallow them whole! Heehee, I like that part! I know it’s tricky and might sound downright mean, but it’s how I make a living.
Glowing in the dark,
We’re at Marion Rise on the Southwest Indian Ridge, a mid-ocean ridge located along the floors of the southwest Indian Ocean and the southeast Atlantic Ocean (yellow in the diagram below). The ridge is a plate boundary where plates are moving away from each other, so it’s called a divergent boundary. This ridge is considered ultra-slow spreading because the plates move away from each other at rates of only 1.4 to 1.5 centimeters per year- that's slower than your finger nail grows. Fast spreading corresponds to speeds of more than 7.5 cm per year and slow corresponds to speeds of less than 5.5 cm per year. At the Marion Rise the rate is only 1.4 cm per year. Now that’s slow! It’s one-tenth the speed of the speed at Pito Deep where I was two years ago. This is an ultra-slow-poke.
At mid-ocean ridges, the Earth's tectonic plates are pulled apart allowing the Earth’s mantle to rise up. Because this mantle is hot, it is less dense and more buoyant and so forms the raised area or ridge where the plates meet. As the plates pull apart the Earth's crust cracks, and hot magma bubbles up to fill the cracks and spills onto the surface where it is cooled by ocean water forming new ocean floor. At the same time across the ocean, the other side of the plate could be subducting under continental crust. That means that where oceanic plates and continental plates push against each other, the oceanic plate moves underneath because it is denser. As gravity pulls it down, the whole plate is pulled away from the mid-ocean ridge. The older crust descends to depths of 600m deep into the mantle. This means oceanic crust is rapidly (on a geological time scale) recycled back into the mantle. Rocks of the ocean floor are young whipper-snappers compared to rocks on land. The oldest ocean floor crust is only about 200 million years old, but there are rocks on land as much as 4 billion years old!
Remember what I told you about the striped ocean floor? Well, magnetic minerals will record the direction of the Earth’s magnetic field as magma cools to become rock. When the Earth’s magnetic field reverses and our magnetic north pole becomes a magnetic south pole, any new magma will cool and record this reversed magnetic field. That’s how the stripes are made!
Wow. That was deep!
Slackjaw Sally here with more instrument deployment news! Along with turning on the multibeam, when we’re in international waters we pull a magnetometer (Maggy) behind the ship. Maggy measures magnetic field strength and detects variations in the magnetic field of the seafloor. A stronger magnetic field could be due to a sunken ship made of steel, or a rock formation containing grains of magnetite. Scientists use magnetic data to identify important archeological sites and to estimate the age and thickness of volcanic lava flows at mid-ocean ridges. Engineers use magnetic data to locate pipelines, undersea cables and bridge foundations.
How can magnetic data help us estimate age? Believe it or not, the ocean floor is striped. What!? Striped? No, not like black and white or colored stripes you see with your eyes. These are stripes of normal and reversed polarity of the magnetic field recorded by magnetic minerals in the lavas of the ocean floor. Where do these stripes come from? As new lava cools, the magnetic minerals in it record the current orientation of the Earth’s magnetic field. When the Earth’s magnetic field changes, the minerals in the new lavas record the new orientation of the field, but the old lava is already frozen solid and retains the orientation of the old magnetic field. Scientists map the magnetic stripes using data from magnetometers pulled behind boats, or in submarines run close to the seafloor, which determine the direction of magnetic field in the rocks. The nearly symmetrical pattern of stripes moving in both directions away from the mid-ocean ridge is a time stamp of the magnetic flip-flops or reversals which our planet has seen. There have been about 170 magnetic flip-flops in the last 76 million years. These stripes help geologists figure out how fast the tectonic plates are moving over our planet.
The magnetometer is used to find the stripes. Maggy is a cylindrical, 1-meter-long instrument pulled behind the ship on a cable about three times the length of the ship (to avoid magnetic effects of the ship). Maggy has a chamber filled with hydrogen-rich liquid, like kerosene or methanol, and a power source. A magnetic field is applied to the liquid to spin the protons and when that magnetic field is turned off, the protons spiral back to alignment with the Earth’s geomagnetic field. Maggy measures the frequency of proton spiraling to calculate the total geomagnetic field. As an Overhauser magnetometer, Maggy can resolve the magnetic field into vectors of strength, inclination (angle of the magnetic field line’s intersection with Earth’s surface) and declination (angle from geographic north). This allows Maggy to measure the strength and the direction of the magnetic field as we move along above the ocean floor.
Take a look at the figure below to see how the magnetometer data lines up with the magnetic stripes on the seafloor. When the red line is above the dotted line, the magnetic field is in the normal direction and when the red line is below the dotted line, the magnetic field is in the reverse direction. A normal field is what we see today.- our compass needles point towards the magnetic north pole. If the field were to flip, those needles would point towards our current magnetic south pole.
I’ll be back with more about spreading seafloors tomorrow. Right now, I’m feeling a magnetic attraction to snacks.
Your munch magnet,
We made it to international waters last night and dove right into mapping. The ocean is so vast that very little of its floor has been mapped. Whenever this ship crosses the ocean, it turns on a sonar device attached to the bottom of the ship to collect information about the water depth and the shape of the seafloor. This information is shared world-wide to map the entire ocean floor. We’re collecting seafloor data using the ship’s built in multibeam echosounder.
Multibeam is a type of sonar used to map the seabed. It’s called multibeam because it sends out many beams of soundwaves at once to cover a wide section of the seabed as the ship passes over. Take a look at the artist’s conception of multibeam sonar in the image below. The device is mounted to the hull of the ship and emits soundwaves in a fan-shaped pattern. The soundwaves bounce off the seafloor back toward the ship. The time it takes the soundwaves to hit the seafloor and bounce back to the ship is measured and used to calculate the depth of the ocean floor below the ship.
The receiver can interpret many soundwaves at once because it uses beamforming. Beamforming controls the phase (timing) and amplitude (wave height) of the signal at each transmitter, creating many unique signals, so the receiver can determine the direction as well as depth. Computer software processes the information in real time generating colored maps as the ship moves along. Red represents shallow depths and blue or purple represents deeper areas. The multibeam topographic maps have a resolution of about 60 meters and are used to locate areas of interest for further exploration.
Slackjaw Sally here, writing from the Research Vessel Thomas G. Thompson. I’ll admit that I really enjoyed sunbathing in South Africa and seeing the sites, but I’m glad to be back onboard a research vessel. It’s been two years and I missed the excitement of exploration.
We’re on our way to the Marion Rise in the Indian Ocean, south of Madagascar. Our study site is on the southwest Indian Ridge from 39⁰ to 47⁰ E. I’m with an international team led by scientists from the United States (Henry Dick), China (Huaiyang Zhou) and Germany (Jürgen Koepke) and including researchers from China, England, Germany, Indonesia, Italy, South Africa and the United States. Luckily for me, everyone speaks English! It’s fun hearing all the different accents.
The Marion Rise is an enormous area of elevated seafloor and we’re here to find out why it was uplifted. Available evidence about Marion Rise geology indicates that it is very different from the better-known Icelandic Rise on the Atlantic Ridge. The Icelandic Rise demonstrates extensive volcanism, suggesting that it was pushed upward by a large, hot, mantle plume, but the Marion Rise is a region with limited volcanism. So, what’s going on? How could this area be uplifted so high when its geology is so different? These intrepid scientists seek to find out.
We’ll map the topography of the sea floor under our path using the ship’s sonar to make 60-meter resolution maps in two previously unexplored areas. The Sentry autonomous submarine will be used to map regions of interest within these areas at 1 to 2-meter resolution. These maps will help us decide where to collect rocks by dredging- literally by dragging a wire basket across the sea floor. We’ll collect geophysical information (gravity/magnetics) using instruments from the ship. Of course, we’re also hoping to discover new hydrothermal vent systems while we’re out here.
Co-Chief Scientist Huaiyang Zhou leads an early morning Tai chi session on the fantail, during transit.
Chris Dorn, one of the watch-standers- hard at work