Questions tagged [ocean-currents]

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28 votes
1 answer
43k views

What is responsible for the underwater waterfall illusion of Mauritius Island?

From an aerial view just off the island of Mauritius, there is what appears be an underwater waterfall. The picture below illustrates this visual phenomenon: The image can also be seen from the ...
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16 votes
2 answers
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Great Pacific Garbage Patch Equilibrium Points

I was watching the science channel yesterday and the program mentioned the Great Pacific Garbage rim. I was struck by the illustration (and pretty much every subsequent animation/picture I've seen now ...
16 votes
2 answers
850 views

How does remote sensing of ocean currents work?

I am aware that techniques exist for measuring surface currents using HF radar, either from land-based installations or from space. How do these work? I have assumed in the past that it's some sort ...
15 votes
4 answers
9k views

Is there a way to find the direction to land in the middle of an ocean?

Can I find the direction to land when I am in the middle of the ocean and can not see any land? This is a theoretical question. Any method that doesn't use over-technical methods such as smartphones ...
14 votes
1 answer
2k views

What is the force imposed by underwater currents?

I would like to calculate the force of an underwater current on a meter by meter plate (or any other unit that you may use to represent it) that is standing in front of the current. How do I calculate ...
14 votes
1 answer
270 views

Odd structures in 66 year NCEP daily temperature reanalysis

I have done some simple analyses of historical surface temperature from the NOAA NCAR/NCEP reanalysis (downloaded from ftp://ftp.cdc.noaa.gov/Datasets/ncep.reanalysis.dailyavgs/surface/air.sig995.*.nc)...
13 votes
2 answers
1k views

Forecasting oceanic rogue waves

A rogue wave is, according to NOAA, "a large, unexpected and dangerous" oceanic wave. These are also known as 'killer' or 'freak' waves and have been a part of folklore of the past and observation of ...
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13 votes
2 answers
282 views

Did the formation of Panama trigger the beginning of Ice Ages?

I have been studying ocean currents and associated energy flows in the eastern Pacific and western Atlantic oceans. I also looked at El Nino cycles. I also noted when the large glacial periods ...
12 votes
2 answers
395 views

How stable is the Gulf Stream? Could it stop suddenly?

I'm not completely clear on what Western intensification means, but it looks like a pretty powerful (combination of) forces that presumably wouldn't be likely to change on a timescale of years (or ...
12 votes
1 answer
2k views

Why is ocean surface velocity around 3% of wind velocity?

Many introductory level textbooks suggest that, as a rule of thumb, the velocity of the ocean surface is around 3% the wind velocity at 10 meters above the sea surface. For instance, Ocean ...
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12 votes
1 answer
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What is the (average) velocity of ocean currents?

Does anybody know where to find statistical (average, standard deviation) data on velocities of ocean currents, such as Equatorial countercurrent North of Madagascar Agulhas current East Australia ...
12 votes
1 answer
387 views

What is the area with the largest velocity vertical shear in the ocean?

While there are areas with really strong tidal currents in the ocean, these currents tend to be primarily barotropic. My question relates to the largest vertical difference in velocity and it is ...
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11 votes
2 answers
367 views

What causes these odd-looking currents in the Tasman Sea?

I was looking at the model ocean current maps from earth :: a global map of wind, weather, and ocean conditions for 2015-10-07 00:00 UTC and there are a lot of odd-looking 'whirlpool' areas off the ...
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11 votes
1 answer
282 views

Is there conclusive evidence for the Antarctic Circumpolar Current developing after the glaciation of Antarctica?

The Antarctic Circumpolar Current (ACC) is the continuous oceanic current that encircles the Antarctic continent, as is often explained in the literature as being the cause of the onset of glaciation ...
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11 votes
1 answer
175 views

What efforts have been made to separate the microseismic events related to wind-related ocean waves from the components of volcanic origin?

I have read the question What generates the microseism? and it's accompanying answer. In [#1, cited below], they use the azimuth values of seismographic activity on the flanks of the volcano ...
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11 votes
1 answer
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Use of Neodymium in Paleoceanography

$\varepsilon_{Nd}$ (i. e. the relative deviation of $\frac{^{143}Nd}{^{144}Nd}$ from a standard) is often used as a proxy in paleoceanography to identify the basin of origin of oceanic currents. But ...
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10 votes
1 answer
11k views

What visual wave behaviour help to tell if a tide is going in or out?

I have always wondered how someone could tell, by a brief observation (a few minutes at most), whether a tide is receding or advancing on a rainy day. Assuming there is no access to tide times and ...
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10 votes
1 answer
855 views

Does bathymetry affect ocean topography/height?

Here is a map of ocean surface height or topography: Source: http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2010/12/mean_dynamic_topography_of_global_ocean/9930795-2-eng-GB/...
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10 votes
2 answers
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How to measure ocean vertical velocity?

While horizontal velocities in the ocean are relatively easy to measure, what methods are available to measure vertical velocities? Is there some indirect way to estimate vertical velocities from ...
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10 votes
0 answers
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How much does the Meridional Overturning Circulation strengthen the Gulf Stream?

While the Gulf Stream is a western boundary current (WBC), one professor told me that the Gulf Stream is stronger than it should be just by using theoretical calculations of WBC. How much is the heat+...
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9 votes
1 answer
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How authentic was the movie scene in "The day after tomorrow" related to the understanding of the north Atlantic current system?

Today's The Guardian headline was that Climate crisis: Scientists spot warning signs of Gulf Stream collapse. It reminded an old movie called "The Day After Tomorrow", which suggested the ...
9 votes
1 answer
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How is the distribution of Argo floats managed over the Earth's oceans?

The BBC News article Climate change: Oceans 'soaking up more heat than estimated' mentions Argo floats as one technology to measure the temperature of the oceans, and links to argo.ucsd.edu where ...
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9 votes
1 answer
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How much is Iceland/Norway/Western Europe warmed up by the Meriodional Overturning Circulation?

A shutdown in the circulation was associated with the Younger Dryas stadial, also referred to as the Big Freeze, so I'm curious how much warmer Western Europe is due to the MOC, and how much heat (in ...
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9 votes
1 answer
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How much has the total transport of the Antarctic Circumpolar Current changed over time?

The Antarctic Circumpolar Current (ACC), the oceanic current that flows around the Antarctic continent, has many links to weather and climate processes (e.g., Is there conclusive evidence for the ...
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8 votes
2 answers
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Why is Somalia so dry?

Most deserts are a result of the rainshadow effect, cold currents, the subtropical ridges, or a combination of those. Knowing this, how is the Somali desert caused? It is notable since it has a desert ...
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8 votes
2 answers
126 views

What goes into a tide power prediction for every fifteen minutes over the next twenty five years?

I was watching a segment about tidal power generation on a PBS NewsHour broadcast. I've set the time code at about 11:45 to capture a little background. This bit ...
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8 votes
2 answers
331 views

How does heat get transported between the surface layer, twilight zone, and the deep ocean?

Just as importantly, how do we measure the heat that's transported from the surface layer into the twilight zone and deep oceans?
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8 votes
1 answer
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What is the relationship between Ekman transport and Ekman pumping?

Ekman transport is the integrated horizontal flow in the boundary layer resulting from the balance between frictional forces (at the surface or bottom) and Coriolis. Meanwhile, Ekman pumping is a ...
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8 votes
1 answer
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How to Calculate the Equilibrum Function for use in Tide Calculations using Harmonic Constituents

I have found a wealth of information using Harmonic Constituents to calculate tide levels. H(t) = Amplitude * cos ( t * harmonicSpeed + phase lag). Yet when I try to apply this to constituents from ...
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7 votes
2 answers
6k views

Thermohaline: Why is cold and dense seawater salty when warm water holds more dissolved salts?

I read that thermohaline circulation is caused by cold and saline water sinking, while warm and less dense water rises. link I understand that saline water is more dense, as there is a higher mass ...
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7 votes
2 answers
321 views

What mechanism is used to measure ocean currents from cables?

The volume transport of the Florida Current (one of the parts of the Gulf Stream) is measured using an underwater cable. What are the processes that allow for these measurements? How can we obtain ...
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7 votes
2 answers
754 views

How are chenier ridges and strand plains formed at wave dominated coastlines?

In the attached image, we can see chenier ridges and strand plains. How are they formed and what is the involvement of rip and longshore currents in their formation?
6 votes
1 answer
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ocean current frequency

In this paper by Muller and Garrett it is stated: It is a standard expectation that currents in the ocean interior with frequencies much less than the Coriolis frequency will lead to an Ekman ...
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6 votes
1 answer
122 views

Why does the meridional overturning circulation take the convoluted path that it takes?

Why does it take the very weird loop that it takes in the Pacific Ocean? And also in the Indian ocean too?
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6 votes
1 answer
64 views

Can up-welling water at oceanic fronts be physically felt?

If you were swimming/floating within a body of water experiencing upwelling due to sea-surface thermal fronts, would you be able to physically feel the water that is being up-welled or is it on a ...
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6 votes
1 answer
349 views

how old are the gulf stream and the NAC?

After reading about the NAC (North Atlantic Current) weakening in the news, we got to wondering about its history and that of the gulf stream. Specifically, how and when did they start? Were there ...
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6 votes
0 answers
328 views

Why do Mediterranean main currents surrounding landmasses turn counter-clockwise?

At North Hemisphere, main superficial currents turn clock-wise, because of Coriolis Effect. I would expect on Mediterranean Sea to have currents turning in the same sense, but, surrounding landmasses,...
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6 votes
0 answers
82 views

Relationship between obliquity, antarctic circumpolar current, and atmospheric $\ce{CO2}$

Hannah's text on the biology of climate change appears to suggest that forcing due to changes in obliquity can act in opposite ways in Antarctic waters. On one hand, "Low obliquity brings cool ...
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6 votes
0 answers
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What would the climate be like on an Earth-like planet if it had only one convection cell per hemisphere?

Earth has three convection cells per hemisphere. These are the Polar cell, Ferrel cell and Hadley cell. These create the trade winds, westerlies and polar easterlies which control many aspects of ...
5 votes
1 answer
291 views

Does the California cyclone change the California current?

I opened windy.com for the California area and I found that the California current is displayed in the opposite way - from south to north. Is it affected by the recent cyclone or am I misunderstanding ...
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5 votes
1 answer
64 views

Indonesian Throughflow and currents map

According to Wikipedia, Indonesian Throughflow passes Lombok Strait from north to south bringing water mass from the Pacific Ocean to the Indian Ocean. But when I the checked currents map on windy....
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5 votes
1 answer
695 views

What are the effects of underwater "windmills"?

Most early examples of tidal energy generators used barrages (damns) to generate electricity (La Rance, Kislaya Guba, Annapolis Royal). Meanwhile, a lot of newer projects use rotary blades in the ...
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5 votes
1 answer
434 views

Why does wind blowing against a strong current create way bigger waves?

It's a well known fact that wind will cause very big waves if blowing against a strong current, for example in the gulf stream off the US coast, or in the bay of San Francisco with a very strong (5 ...
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5 votes
1 answer
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Why don't Antarctic waters have more upwellings, when Arctic waters are so rich in upwellings?

Formation of ice and hence more dense saltwater sinking happens in both polar regions, creating downwellings. Meanwhile, only a few spots in Antarctica have upwellings I refer to this image: https://...
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5 votes
1 answer
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Guinea Current existence in the Atlantic

Why does the Guinea Current exist at all? There are no similar currents in the Pacific or Indian Oceans and the Guinea Current also disappear during northern summers. Why?
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5 votes
1 answer
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Depth of the wind-induced currents and the shoreline

In the open sea the speed of the current in the developed sea can be estimated as 3% the wind velocity at 10 meters. Why is ocean surface velocity around 3% of wind velocity? Is there a similar ...
5 votes
1 answer
657 views

Is the gulf stream both a wind-driven current and part of thermohaline circulation?

Currents are formed in 3 major ways: Tidal Currents Wind-driven Currents Thermohaline circulation I've seen the gulf stream mentioned as both a wind-driven surface current and being part of the ...
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5 votes
0 answers
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Is there a correlation between the underwater geological activity and topology of the mid Atlantic ridge/ South American plate and the Gulf Stream?

I just had a little eureka moment! I was looking again at this mid atlantic ridge along the western edge of the Eurasian plate. https://en.wikipedia.org/wiki/Lists_of_volcanoes How it and the way it ...
5 votes
0 answers
136 views

Stream function on a periodic domain?

Part 1 In this paper the authors calculate the barotropic stream function from an output of a numerical model as: $$\psi(x,y)=\int_0^y\int_{-H}^0u(x,y',z)~dz~dy'$$ over a global domain and this is ...
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5 votes
0 answers
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Does the Labrador current affect North Atlantic climate?

This summer has seen very low sea surface temperature anomalies in the North Atlantic. Using animations of these over the last year I feel the runoff of freshwater from Hudson Bay, into the Labrador ...
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