# What is Sea level: Definition and 52 Discussions

Mean sea level (MSL) (often shortened to sea level) is an average level of the surface of one or more of Earth's bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead the midpoint between a mean low and mean high tide at a particular location.Sea levels can be affected by many factors and are known to have varied greatly over geological time scales. However, 20th century and current millennium sea level rise is presumed to be caused by climate change, and careful measurement of variations in MSL can offer insights into ongoing climate change.The term above sea level generally refers to above mean sea level (AMSL). The term APSL means Above Present Sea Level, comparing sea levels in the past with the level today.

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1. ### B Coefficient of friction in sea water

Is there any friction coefficient in the sea as there is in ground? I've tried searching but I see results between 0.4 and 25.7 (?). If there's no such thing as a coefficient of friction to water, how do I calculate the amount of force to start moving a X mass object in water?
2. ### What does gravity have to do with sea level?

https://www.physicsforums.com/threads/what-is-sea-level.13108/post-136240 As far as I understand the sea level is the level of the sea water above the geoid or surface of the earth. The level of sea is same everywhere around the world because its all connected. So to calculate the global sea...
3. ### Looking for formulations used in sea level calculations

Hello all, I've been on the hunt throughout the scientific literature for a little while now for some information, but I'm coming up empty. I'm hoping there's some expertise here in the area of altimetry as it relates to sea level calculations. More specifically, I'm trying to find the actual...
4. ### I Air density with a significantly higher sea level

2 scenarios: 1) Situation in the movie "2012", where volume of ocean water hasn't changed, but worldwide seismic activity has caused massive tidal waves. In one scene, a ship is sailing by Mt. Everest close to its peak. In such a scenario, I believe the air density outside the ship would the...
5. ### B 100sqft wormhole from sea level to outer space?

Hypothetical scenario and I'm trying to understand the velocity of the air as it tries to equalize with a large vacuum. I presume this model isn't very much different from an initial loss of 1 atmosphere pressure in space via some puncture. I'm mainly concerned with the immediate wind speeds and...
6. ### I Spacetime Geodesics at Sea Level & Zoomed Out

I suppose that that a spacetime geodesic of an object falling on Earth would a appear as straight line. But what I'd like to see is a whole bunch of relevant geodesics that would represent falling bodies all around the Earth such that one could zoom out and so see these straight line geodesics...
7. ### B Melting Ice Caps and Sea Level Rise: Separating Fact from Fiction

I'm pretty sure that everyone knows that if you put an ice cube in a cup of water, and leave it for some time for the ice to melt, the level of water in the glass will not rise. (you could use that principle where that guy was in the tub and said "Eureka!" and then ran around naked). Now, my...
8. ### Volume expansion and sea level rise

Homework Statement [/B] Oceans cover 2/3 of the earth’s surface, with an average depth of 3.7 km. The average surface temperture is 17◦ C. Taking this temperature as representative of the entire ocean, and knowing that the coefficient of volume expansion for water at this temperature is β = 1.7...
9. ### 42% of Sea Level rise due to human water use?

I was surprised to see this in a 'pop science' article a few years ago ("Ask Marilyn"), but quickly found the source, which appeared reputable (to me). But I have not seen any follow up. I finally got back to it. https://www.nature.com/articles/ngeo1476 To stay within forum guidelines, please...
10. ### Sea level

The channel minutephysics explains the concept of sea level. Though it seems a pretty straightforward concept, actually, there is something more people don't know.
11. ### Potential Energy Problem -- GPE of a person at 5334m above sea level

1. With an elevation of 5334 m above sea level, the village of Aucanquilca, Chile, is the highest inhabited town in the world. What would be the gravitational potential energy associated with a 64.0 kg person in Aucanquilca? Assume that the free-fall acceleration at Aucanquilca is equal to that...
12. ### B Energy Requirement to Levitate 550 lb Mass at Sea Level

To maintain a 550 lb mass in the air not touching the ground at sea level (radius of Earth is 4000 miles), what is the expenditure of energy required given perfect efficiency of the process?
13. ### Writing: Input Wanted What if sea level rose dramatically?

I'm working on an idea set on an Earth where the ice caps have melted. I'm curious about New York City in particular, how far Manhattan would be from the new coastline, how many towers would still poke up out of the Atlantic and how much would still be above water. Also curious where the best...
14. ### I Why Sea Level sometimes gives an illusion being at height

Why Sea Level sometimes gives you an illusion being at height like a small mountain? Specially when you are driving down of the mountain? Please find the attached image to see what I am referring to.
15. ### Reduced Efficiency at Sea Level

Liquid-fueled rocket engines almost always seem to have lower specific impulse at sea level than in a vacuum. I know of one reason: 1. Nozzle expansion. Many engines are optimized for higher-altitude performance, so their nozzle is over-expanded for lower altitudes. I would say more, but I...
16. ### Problem: using thermal expansion to calculate sea level rise

Homework Statement Since the 1980's a total of 20 x 10^22 J of additional energy has been absorbed by the worlds oceans. This is 90% of the additional heat our planet is storing as a consequence of global warming. The surface area of the worlds oceans is 361,900,000 km^2 and we will assume this...
17. ### Would a 10km/s projectile disintegrate at sea level?

Assuming you could fire a projectile at 10km/s. Polished aluminum, almost solid, same size and shape as an artillery shell. Most people say it would disintegrate due to the friction at sea level. But would it really? I heard someone say it would just ablate some of the aluminum. And that 1700...
18. ### Sea level change as ocean surface warms

Homework Statement I am attempting to replicate the IPCC estimates of the amount of sea level rise due to thermal effects on the seawater. The earth, black-body temperature is 16C but there are projections of a 1C increase in less than 100 years. Ignoring ice melt and land flooding, how much...
19. ### Thermodynamics: Air pressure at 3000m above sea level

Hello all! Can you please provide some guidance with this problem? 1. Homework Statement Calculate the air pressure at 3000m above sea level assuming that the molecular weight of air is 29 and the ambient temperature is constant against height. Homework Equations Stokes-Einstein equation. In...
20. ### GPS Altitude Mystery at Sea Level - Solved?

I'm a programmer/electronics student and I recently bought a GPS which I hooked up serially with my laptop. I didn't get into much detail of encoding the string which is output from the TX/RX pins of the GPS so I downloaded, a ready made program called "ublox 6". Longitude and latitude are...
21. ### Sperm Whale says hi at 600m below sea level

Scientists operating an underwater ROV had a fantastic surprise when a sperm whale decided to come and check out the machine. Fantastic images and from nearly 600m below sea level!
22. ### How wide is the observable horizon, at sea level?

I'm quite aware of how to compute how FAR you are from the horizon, but my question is, how WIDE is the observable horizon at sea level (like, from left to right, how many kilometers is this): http://www.jeicentral.com/wp-content/uploads/2014/10/far_sunset_in_te_ocean_horizon-wide.jpg Thanks!
23. ### Rise in sea level due to increased temp. on earth

Homework Statement See attachment Homework Equations See attachments The Attempt at a Solution I'm really struggling to understand how to solve this problem. I guess I need to know the volume and surface of the sea on earth? But I'm honesty a bit lost as we don't have a...
24. ### What is causing the annual variations in sea level in the Florida Keys?

In southern Florida, and especially in the Florida Keys, there are some very shallow areas that make it very obvious how low low-tide is. I'm stumped to notice that there seems to be significant variations from year to year. For example, an area we call the flats is normalls under six...
25. ### Line of sight propagation when land is 700m above sea level

Homework Statement A 200 MHz signal is to be transmitted over a point-to-point wireless link. Assume the earth’s surface is flat over the entire propagation distance, and is 700 metres above sea level. The transmitter is at ground level, and the receiver is situated on top of a multi-storey...
26. ### Effects on a cable at sea level compared to 35,000 feet

Hi Guys, Struggling to find any information on the changes to a cable at altitude compared to at sea level. The initial task was to calculate the resistance of generator wires and then change them from copper to aluminium cables to save weight. I have done this leading me onto describing the...
27. ### Atmospheric Pressure Above the Sea Level

Homework Statement The atmospheric pressure deceases exponentially with height. At 5.5 km, the pressure is half that at sea level. At what height is the pressure one eighth that of sea level? Homework Equations All I can think of is Pat=ρgh I know 1 atm=101325 Pa=101.325 kPa and that this is...
28. ### What is the expression for air pressure below Earth's surface?

If you were to drill a hole in the ground, what is the expression for the air pressure below ground? Above ground it is exponential with distance (at least to an approximation), so what is it for below Earth's surface? It has to increase but probably with a lesser absolute slope than above...
29. ### Volume of a mole of air 15km above sea level

Homework Statement one mole of an ideal gas takes up 0.0225m3 at 0 degrees celsius and 1.01x10(5) pascals. (calculated) hence, calculate the volume of 1 mole of air (ideal) at an altitude of 15km above sea level. average molecular mass of air = 29 amu. T @ altitude of 15km = 0 degrees C...
30. ### How do I find my height above sea level?

I'm under the impression that this takes special equipment? We're talking centimeter precision by the way. Shouldn't I be able to get this from some App by now?!
31. ### Change of sea level in relation to sea ground

My physics teacher said that if the sea ground is higher, then, because of the stronger gravitational force, the sea level is lower. I am not sure if this is true and he didn't give a very strong proof. I thought sea level equalizes all over the earth. Of course I am taking the sea level in...
32. ### What happens with the sea level due to the centrifugal acceleration?

What happens with the sea level due to the centrifugal acceleration?
33. ### Question about calculating time dilation of clocks at sea level

I am trying to understand how relativity explains that clocks all over the globe count at about the same rate at sea level. One of the papers that I have looked at is "The global positioning system, relativity, and extraterrestrial navigation" at...
34. ### What Causes the Rapid Changes in Sea Level?

There is in the past significant very rapid rises and falls of sea level. As there is no mechanism to rapidly melt and reform ice sheets to explain the sea level rise and fall based on mass balance (more or less water in the ocean) specifically what is causing the rapid changes in sea level is...
35. ### The partial pressure of gases below sea level?

Hello everyone, The partial pressure of the atmosphere 33 feat benath the surface is doubled the normal amount. (2x760 mmHg). I can understand how lower you go down higher the pressure but I don't understand how you can measure atmospheric pressure under the sea. I mean under the sea you got...
36. ### Measuring Sea Level: Tides, Elevation & Distance from Earth's Center

Is there a median sea level that the logs of sea level data is based? I know the moon causes the tides which upsets the equilibrium on a constant basis. I need this sea level to be based upon the distance from the center of the Earth so with the elevation of a particular city on the Planet...

Might we be near the end of a large cyclical regression; not so different from Permian end regression? Statistically might it not seem more likely that we are due to revert at least towards an average of sea level for overall Phanerozoic http://en.wikipedia.org/wiki/Phanerozoic" , or even a...
38. ### Accurate Height(above sea level) Measurement Device

Hi Guys I am new engineering and would appreciate any advice or ideas on this project. I need to measure the height above sea level of a small vehicle that I am building.. My first idea was GPS, but the vehicle is going travel under a thick steel structure, so it will not work. I thought...
39. ### Clock precision as a function of temperature and height above sea level

Homework Statement A grandfather pendulum clock is to be moved from a location at sea level to a new location approximately 200 m up in height. We assume that the Earth's radius is 6400 km. We know Newton's gravitational law and the oscillation equation for a pendulum. (*) How much...
40. ### Sea Level Rise: New Measurements from GRACE Satellites

There is a new paper about it, the results of the measurements of the GRACE satellites on the sea level changes. http://sciences.blogs.liberation.fr/home/files/Cazenave_et_al_GPC_2008.pdf Good news.
41. ### Column of Mercury at Sea Level

Homework Statement At sea level, the pressure of the standard terrestrial atmosphere will support a column of mercury of density 1.359 x 10^4 kg/m^3 and of height 0.7600m at a place where the acceleration due to gravity is 9.80665 m/s^2. Show that 1 atmosphere = 760 mm Hg = 1013hPa. I...
42. ### Global Warming Impacts on Earth's Sea Level, Ocean Circulation, Oxygen Isotopes

how would the Earth be affected by global warming in terms of the sea level , global ocean circulation, and oxygen isotopes?
43. ### What Causes 430,000 Year Cycles in Paleocene Sea Level?

We have discussed sea level yoyo's from the Pleistocene ice age of which it is suggested that it balances with the ice volume paced on the poles. So all of a sudden a study pops up (courtesy of the author), Dr Madeleine Briskin...
44. ### Seaport 2.5 Miles Above Sea Level(?)

"Seaport" 2.5 Miles Above Sea Level(?) Two days ago I discovered a new issue for me--Expanding Earth. Yes, I know there are pros and cons to plate tectonics and expanding Earth but each is a theory. The below story has bothered me for years but I felt the Earth may have contracted causing...
45. ### Calculating Mach Number of Aircraft at Sea Level

Homework Statement What is the mach number if an aircraft traveling at sea level at 0 degrees with a speed of A)1140km/h b)900.0km/ the answers are 0.995 abd 0.753 in order. I Cant get those. Homework Equations mach number=speed of object/speed of sound The Attempt at a Solution...
46. ### How to measure height above sea level

When drawing sewer pipes, I often include the height above sea level within one centimeter to get the correct fall, simply cause I've been told to do so. I'm just curious as to how this height is actually measured by the people who actually lay these pipes? Is there some kind of instrument that...
47. ### Why is the Arctic sea level dropping while global sea levels are rising?

I was quite surprised by all this. With global warming ice is melting, and sea levels in general are going up. Why should the Arctic be any different :confused:
48. ### Speed of Sound & Light at Sea Level

I want to know the speed of sound at sea level. :confused: I also want to know the exact speed of light in kilometres. :confused:
49. D

### Calculate Sea Level Rise: Find Realistic Estimates Based on Scientific Formulas

Hello, all. Neat site! I'll be using it. Not to upset anyone, but being an Environmental Scientist for 15 years the "predictions" of sea level increases by GW that I was hearing seemed totally unrealistic to me, even just on the most basic level. Recently I heard one of the hosts on the...
50. ### What were the consequences of the 1953 hurricane in the Netherlands?

Monique – under the sea level :( Key findings of the Pentagon: … By 2007 violent storms smash coastal barriers rendering large parts of the Netherlands inhabitable. Cities like The Hague are abandoned… http://observer.guardian.co.uk/international/story/0,6903,1153513,00.html...