#ocean physics

[eddieintheocean]

Terrible news..... physics and mathematics..... in my marine biology degree......

[scienceguy22]

Robots imitating lampreys.

Lampreys are jawless, eel-like fish, one of the most ancient vertebrate lineages on Earth, existing for more than 360 million years—far older than dinosaurs. These animals represent the earliest stages of vertebrate evolution, before jaws, paired fins, or bony skeletons evolved. The mouth of the lamprey is based on a new robot that was made in China this month. This robot is well-suited to cross-media robotics, meaning it can operate in both air and water. The robot has a suction disc modeled on the lamprey's mouth, allowing it to grip objects both in the air & underwater, even on rough, porous, or moving surfaces. The key innovation is a hybrid adhesion mechanism that combines soft shape-changing structures & pressure differentials. This seal prevents water from gushing in & breaking suction, maintaining a tight seal.

It can surprisingly lift quite a lot. The gripper weighing 50 g (1.76 oz) can lift 93.7 lbs (42.5 kg). This is astonishing for a soft robotic device. The key differences between a lamprey's mouth and the robot's underwater gripper are that the robot has no teeth, while the lamprey's teeth dig into the surface. The lamprey actively pumps water out of the mouth, while the robot has a shape-memory polymer. The robot can work in both air & water, while the lamprey is strictly underwater. The robot can also increase its grip pressure.

It is designed to be used for picking up objects, tools, debris, or sensors. Also, attaching sensors to animals without harming them. Handling wet or porous materials where suction normally fails. In tests, it was able to pick up a 0.01 g (0.0003 oz) microelectronic chip up to an 11.4 kg desk (25 lbs). Underwater, it adhered to coins, red bricks, scallop shells & conch shells. The lamprey-like disc was mounted on a robotic arm & used it to handle a bionic manta ray robot. The arm picked up the robot in the air, lowered it into a tank, released it to swim, & then reattached to it again underwater before lifting it back out. The robot will be useful for marine maintenance, deep-sea exploration, & amphibious rescue. It may not be fast, but its reliable gripping dexterity and strength will be essential across messy, real-world surfaces.

[scienceguy22]

How do deserts form next to oceans?

When you picture a desert, you probably imagine a vast, empty landscape far from any water. 3 main factors allow deserts to form next to oceans, & it all has to do with atmospheric circulation (how the air moves vertically & horizontally) & how mountain ranges interact with air moisture. Oceans are moisture factories, but moisture becomes rain only when the air is forced to rise. Warm, sinking, stable air can sit over an ocean coastline & produce almost no precipitation at all. When this occurs, you get a hot, dry desert right beside the ocean. Examples are the Sahara (Atlantic coast), the Arabian Desert (Arabian Sea), & the Australian deserts (Indian Ocean).

Some oceans have cold currents that chill the air, such as the west coast of South America (Peru-Chile), & cold currents can't hold much moisture. At most, they get fog but not rain, which is why some of the driest deserts on Earth are fog deserts. Examples are the Atacama Desert (Chile/Peru) & the Namib Desert (SW Africa). Other deserts are influenced by whether there's a mountain near them. If moist air hits a mountain range, it cools and drops rain on the side hitting the mountain (windward side). The other side of the mountain (the sheltered or leeward side) has the opposite atmospheric effect. After moist air hits the mountains & then rises & cools, it has already rained out on the windward side. The now-dry air crosses the crest & sinks on the opposite side, called the leeward side. Sinking air warms, which reduces relative humidity; clouds evaporate, resulting in no rain. Examples are the Baja California Desert, the Patagonian Desert (Andes), the Gobi Desert (Himalayas), & the Great Basin Desert (Sierra Nevada).

Contrary to popular belief, Antarctica is home to the world's largest desert. A desert is any region that receives less than 10" (250 mm) of precipitation per year. They receive about 50 mm per year coming from interior snowfall, often less than 2 inches. This makes Antarctica the driest desert, the coldest desert, the windiest desert, & the largest desert on Earth (about 5.5 million sq mi (14 million sq km)). The air is too cold and moist, the continent is ringed by winds that scour moisture away & the surrounding ocean & current isolate it from humid air masses. Six major coastal deserts offer trekking, sightseeing (including giant dunes), sunbathing, and an ocean dip. On the Red Sea coast, where desert dunes meet coral reefs, you can include snorkeling as well as trekking & sunbathing.

[scienceguy22]

Meet the Carnivorous Death Ball Sponge! 🧽🌊

Starting with the carnivorous death-ball sponge, the “ball” that is described refers to its spherical shape. It is a brand new species (Chondrocladia species nova), Latin for “new species.” It is one of the 160 known carnivorous sponges, all of which abandoned filter feeding to eat small crustaceans, larvae & small worms. All of these animals have abandoned filter feeding & evolved hooks, sticky filaments, or grasping structures to catch prey. This species’s whole body is entirely covered in hooks. The hooks are made of silica-based spicules, which act like internal scaffolding, letting the sponge maintain shape under the intense pressure at 11,800 ft (2 1/2 miles (3,600 m)) below the ocean. That’s like having a family car resting on every square inch of your body. There’s also no light down there. It’s so dark, like a sealed movie theater with the power cut, under a pressure so high it’s like having a stack of 360 Earth atmospheres pressing down on every part of you at once. And down there, it doesn’t filter water like a normal sponge; it hunts!

Carnivorous sponges have a unique feeding strategy. Their Velcro-like glass hooks prevent prey from escaping. Then specialized cells secrete enzymes that break down the prey’s tissues. Nutrients are absorbed directly through the sponge’s surface. There is no gut; digestion is entirely external & cellular. To reproduce, they release sperm into the water that enter neighboring sponges. Since sponges are hermaphrodites, it doesn’t matter if a sponge is male or female because they can switch between being either male-functioning or female-functioning.

Sponges are long-lived animals, from centuries up to over 1,000 years for some species. Other kinds of sponges have balls on their tips, along their stalks, or grouped together from their bodies like decorations. Their balls also are covered in small silica hooks that snare prey as they brush against them. Even after centuries of scientific exploration, Earth is still full of surprises.

[worldoceansday]

Launch of the Second World Ocean Assessment (WOA II).

Launch of the Second World Ocean Assessment (WOA II)

The Second World Ocean Assessment (WOA II) is launched on 21 April 2021, ahead of the International Mother Earth Day 2021 (22 April). WOA II

The Second World Ocean Assessment (WOA II) is the major output of the second cycle of the Regular Process for Global Reporting and Assessment of the States of the Marine Environment, including Socioeconomic Aspects. It is the newest outcome of the only integrated assessment of the world’s ocean at the global level covering environmental, economic and social aspects. 

WOA II is a collective effort of interdisciplinary writing teams made up of more than 300 experts, drawn from a pool of over 780 experts from around the world. It provides scientific information on the state of the marine environment in a comprehensive and integrated manner to support decisions and actions for the achievement of Sustainable Development Goals, in particular goal 14, as well as the implementation of the United Nations Decade of Ocean Science for Sustainable Development.

Second World Ocean Assessment (WOA II)

Regular Process

[siamkram]

The currents in the ocean are like the curls in my hair...

Rizos en la mar...

Opposing currents in Mona passage.

Image Credit: Ocean Physics Education (Facebook page)

[howstrangethemusicsoundstome]

I’m thinking I should focus on geophysics or ocean physics instead of astrophysics for what I want to do in exoplanet studies. Good thing I haven’t finished applying to grad schools yet.

[oceanograph]

http://scubageek.com/articles/wwwceler.html Water Wave Celerity The three-dimensional behaviour of surface water waves as they interact with wind, bottom, obstructions, currents, and each other is very complex. Much insight into the general behaviour of waves can be obtained by first studying two-dimensional, monochromatic, progressive waves using the so-called small amplitude wave theory. The figure below defines the terms most commonly used in discussions of water waves:. As waves pass some fixed point, the time between consecutive crests is the wave period T. The speed of the wave, or its celerity, C, (as ocean engineers refer to it), is the distance travelled by a crest per unit time, or C = L/T Equation 1 The small amplitude theory requires that both a/L and a/d be small. Using this assumption and solving the equation of motion for small amplitude waves yields the following expression for the wave celerity: Fig. where g is the gravitational acceleration. It is clear from Equation 2 that the wave celerity is a function of both the wave length (L) and the water's relative depth d/L. Since the hyperbolic tangent function (tanh) has simple limiting forms for both small and large values of its argument, it is useful to classify waves according to the relative depth, as follows: Note that in deep water the celerity is independent of water depth, which is not surprising in view of the fact that the waves do not interact with the bottom. What is interesting, however, is that the celerity depends on the wave length. Water is therefore a dispersive medium with respect to deep water surface waves, in much the same way that it is a dispersive medium for light waves. Shallow water surface waves, on the other hand, do feel the bottom, and slow down as the square root of the depth. Their speed is not a function of the wave length. As surface waves travel across various depths of water their period T does not change (for a proof see the article entitled "Constancy of Wave Period"). In deep water, therefore, the wave length is constant, but as waves approach a beach the wave length decreases as the square root of the depth. Wind-generated waves typically have periods from 1 to 25 seconds, wave lengths from 1 to 1000 meters, speeds from 1 to 40 m/s, and heights less than 3 meters. Seismic waves, or tsunamis, have periods typically from 10 minutes to one hour, wave lengths of several hundreds of kilometers, and mid-ocean heights usually less than half a meter. Because of their long wavelengths, tsunamis often satisfy the criterion for shallow-water waves. For example, when a tsunami with a wave length of 200 km passes over a depth of 4 km (the average depth of the oceans) the relative depth is d/L=.02. Since this is less than .05, this tsunami is a "shallow-water wave", and its celerity depends only on the water depth. REFERENCES: Robert M. Sorensen, "Basic Wave Mechanics for Coastal and Ocean Engineers" (John Wiley & Sons, 1993), Chapter 2. Last Modified: 10:11pm , April 28, 19