Tag: ocean

Ocean Mixing
Movement in Earth’s oceans is driven by a complicated interplay of many factors like temperature, salinity, and Earth’s rotation. Above are results from a numerical simulation of the top 100 meters of ocean contained within a 1 km x 1 km box. The colors indicate surface temperature. Two major processes create the motion we see. The first is convection, in which water at the surface releases heat to the atmosphere and cools, causing it to then sink due to its greater density. Warmer water rises to replace it. This process happens quickly and dominates the early part of the simulation where we see the puffy convection cells shown on the left animation.
A slower process is in effect as well. Because of variations in the water temperature, the density of the fluid at a given depth is not constant. We can already see that at the water surface, where the temperature (and thus density) is varying significantly. Those variations in density at the same depth combined with gravity’s tendency to shift fluids create what is known as a baroclinic instability. Put simply, this instability will cause warmer water to slide horizontally past colder water. The result is the large, spinning eddy motion seen in the animation on the right. To see how the whole system develops, check out the full video below. (Image/video credit: J. Callies)
May 9, 2016
Coastal Upwelling
Cool temperatures and abundant nutrients make the waters off the western coast of North America especially biologically productive. This image is a composite of satellite data highlighting large phytoplankton blooms in the California Current. This current runs southward along the coastline, and, like other eastern boundary currents, it experiences strong upwelling, or rising of colder, nutrient-rich waters from lower depths. The upwelling is driven in part by Earth’s rotation. As the earth spins, Coriolis effects push the California Current out from the coast, allowing deeper waters to rise and fill the void. The cooler water provided by the upwelling is a major factor in the moderated climate along the West Coast. (Image credit: NASA/N.Kuring; via NASA Earth Observatory)
April 21, 2016
Fluids Round-up
Time for another look at some of the best fluids content out there. It’s the fluids round-up – with a special focus this week on oceans!
– Ryan Pernofski spent two years filming the ocean in slow motion with his iPhone to make the short film “Slowmocean” seen above. It’s a gorgeous ode to the beauty of breaking waves.
– Oceans with higher salinity than Earth’s could drive global circulation that would make exoplanets more hospitable to life.
– Speaking of alien oceans that could harbor signs of life, there’s discussion afoot of how future missions to icy moons like Europa or Enceladus could collect samples from plumes ejected from beneath the ice.
– Wind and waves make harsh, erosive environments. This photo essay from SFGate shows how greatly the sands of Pacifica shift over time. (submitted by Richard)
Bonuses:
– New research explores how Martian mountains may have been carved out by the wind.
– Ever listened to an orchestra made from ice? You should! Learn about Tim Linhart, who builds and maintains ice instruments. (submitted by ashketchumm)
– MIT has demonstrated a new 3D-printing technique that allows for printing liquid and solid parts simultaneously, allowing would-be creators to rapid-prototype hydraulically-driven robotics.
Even more bonus bonus!
– ICYMI, the new FYFD video made Gizmodo!
If you’re a fan of FYFD, please consider becoming a patron. As a bonus, you’ll get access to this weekend’s planetary science webcast!
(Video credit: R. Pernofski; via Flow Visualization; Pluto image credit: NASA/APL)
April 14, 2016
Rogue Wave Recreated
If you look online, the term “rogue wave” gets thrown around a lot – a whole lot. And most of the videos you see of “rogue waves”, “freak waves”, and “monster waves” are just, in fact, big waves. What makes a deep-water ocean wave a rogue, scientifically speaking, is that it is extreme compared to its surroundings. One definition requires that a rogue wave be more than twice as tall as the height of average large waves in the area – like the rogue that takes out the Lego boat above. Outside the lab, this is a rare event – fortunately – because a true rogue wave has tremendous destructive power and seems to appear out of the blue.
This seemingly unpredictable behavior is thought to arise from nonlinear interactions between waves. Essentially, under the right conditions, a rogue wave grows monstrously large by sucking energy out of other surrounding waves. One way to try and predict rogue waves is to measure all the waves nearby and simulate their potential nonlinear interactions computationally – but this is time-consuming and requires a lot of computing power.
Instead, researchers have developed an alternative method, illustrated in the time series above. Instead of considering the rogue potential for all waves, they identify waves with characteristics that make them more likely to go rogue and focus on simulating those waves. In the animation, the wave packets are colored from green to red based on their increasing likelihood of turning into rogue waves. The algorithm is simple enough to run quickly on a laptop and can provide a couple minutes of warning to a ship’s crew – enough time to batten down before the wave hits. (Image credits: simulation – T. Sapsis et al., source; experiment: N. Ahkmediev et al., source; via The Economist and MIT News; submitted by 1307phaezr)
March 11, 2016
Underwater Currents
Like the atmosphere, the ocean is constantly in motion, churned by currents that often go unnoticed by humans watching the surface. Filmmaker Julie Gautier and free diver Guillaume Néry demonstrate the power and speed of some of these underwater currents in the film above. The footage was shot in Tiputa Pass, part of an atoll northeast of Tahiti. In it, Néry serves as a human-shaped seed particle in the flow, illustrating just how swift the current is. (Video credit: J. Gautier; via Colossal; submitted by jshoer)
February 6, 2015
Below a Surfer’s Wave
From below a plunging breaking wave–the classic surfer’s wave–looks like a giant vortex tube. Smaller rib vortices, the rings around the main vortex in the photo above, can form where there are variations along the breaking wave. As the wave rolls on, it stretches the vorticity variations along the wave’s span. When stretched, vortices spin up and intensify; this is a result of conservation of angular momentum. Check out more amazing photos of waves in Ray Collins’ portfolio. (Photo credit: R. Collins; via The Inertia)
January 28, 2015
Filter-Feeding
Sponges are filter-feeding marine animals that rely on water flow to obtain their nutrients and remove waste. By injecting non-toxic fluorescein dye at their base, one can visualize the flow they induce in the water. Only seconds after the dye is introduced, the sponges have pumped it in, through, and out. Different parts of the sponge filter particles of various sizes for food. Oxygen and carbon dioxide are transported, respectively, into and out of cells via diffusion. In this way, the sponge’s pumping fulfills digestive, respiratory, and excretory functions. (Image credit: Jonathan Bird’s Blue World, source video; submitted by Jason C)
December 8, 2014
Inside the Strait of Gibraltar
When a fluid is stratified into layers, it’s possible to have waves generated and transmitted along the interface between layers. Because these waves remain inside the bulk fluid, they are called internal waves. They often occur in the atmosphere or the ocean as fluids with different properties move past changing terrain. The Strait of Gibraltar is an excellent source of internal waves. The tidal exchange of waters between the Mediterranean Sea and Atlantic Ocean takes place through a narrow corridor interrupted by the peak of Camarinal Sill. The internal waves generated by the constriction are large enough that their effect on the surface flow is visible to satellites. The video above visualizations data from a numerical simulation of flow through the Strait, showing the obstacles, flow, and wave structures generated. (Video credit: J.C. Sanchez Garrido et al.)
October 24, 2014
Phytoplankton Bloom
In satellite imagery the blue and green whorls of massive phytoplankton blooms stand out against the ocean backdrop. These microscopic organisms are part of a delicate predator-prey balance and can be very sensitive to nutrient concentrations and other environmental conditions. Their individual size is negligible, but in a bloom phytoplankton are numerous enough that they act as seed particles for the flow. As a result, differing concentrations of phytoplankton reveal the swirling, turbulent mixing of ocean waters. (Image credit: NASA/USGS; via SpaceRef; submitted by jshoer)
October 9, 2014
Freediving
The freediving del Rosario brothers have created a real treat with this underwater film. There are no computer-generated special effects, just some clever tricks with camera angles, perspective, and buoyancy. The end result is slightly surrealistic and captures some of the fluid beauty of the ocean. And don’t miss the excellent bubble ring vortices. (Video credit: The Ocean Brothers; via Gizmodo; submitted by jshoer)
September 26, 2014