Embed Size (px)
Citation preview
2
Oultine
1/ Physical Properties
2/ Tide
3/ General Circulation
4/ Eddies
5/ Upwelling systems
6/ Mixing in the ocean
3
Reference
4
1/ Physical properties Pressure Temperature (in situ, potential) Mixed layer, thermocline Salinity Density and compressiblity Sound propagation Light propagation
5
FIGURE 3.2
The relation between depth and pressure, using a station in the northwest Pacific at 41° 53’N, 146° 18’W.
TALLEY Copyright © 2011 Elsevier Inc. All rights reserved
Hydrostatic pressure
1dbar ~ 1m
6
Temperature decreases from Eq to Pole.Why?
7
Temperature decreases with depth. The bulk of the ocean is cold.Why?
8
9
Incidentally the energy flux coming from the Sun is balanced by IR flux of equal intensity
10
Thermocline
Temperature seasonal cycle
Mixed layer
11
-
=
T January T July
Seasonal amplitude
12
Salinity (1 psu ~ 1g.kg-1)
Salinity variations are small, but not negligible
13
FIGURE 3.1
Values of density t (curved lines) and the loci of maximum density and freezing point (at atmospheric pressure) for seawater as functions of temperature and salinity. The full density is 1000 + t with units of kg/m3.
TALLEY Copyright © 2011 Elsevier Inc. All rights reserved
Salinity (S) and Temperature (T) control the density (ρ) [kg.m-3]
14
T-S determine « water masses »
(T,S) is a signature of the water origin, e.g. : Mediterranean Water (warm and salty)
15
FIGURE 3.4
Increase in density with pressure for a water parcel of temperature 0°C and salinity 35.0 at the sea surface.
Sea water is compressible
Variation of in-situ density with depth for a given (T-S) = (0°C, 35psu) watermass
16
Potential density removes the effect of pressure.
It can be referenced at the surface (or at any depth)
Potential density referenced at 10km
Potential density referenced at surface
Mariana Trench
17
FIGURE 3.6
(a) Potential density and (b) Brunt-Väisälä frequency (cycles/h) and period (minutes) for a profile in the western North Pacific.
TALLEY Copyright © 2011 Elsevier Inc. All rights reserved
Brunt Vaisala frequency (N) of vertical oscillations
18
FIGURE 3.7
For station Papa in the Pacific Ocean at 39°N, 146°W, August, 1959: (a) temperature (°C) and salinity (psu) profiles, (b) corrections to sound speed due to salinity, temperature, and pressure, (c) resultant in situ sound-speed profile showing sound-speed minimum (SOFAR channel).
TALLEY Copyright © 2011 Elsevier Inc. All rights reserved
Speed of sound ~ 1500 m/s
19
FIGURE 3.8
Sound ray diagrams: (a) from a shallow source for a sound-speed profile initially increasing with depth in upper mixed layer to a shallow minimum and then decreasing, and (b) from a sound source near the speed minimum in the sound channel for a typical open ocean sound-speed profile.
TALLEY Copyright © 2011 Elsevier Inc. All rights reserved
SOFAR channel(p50)
20
Sea Mammal's Greatest hits
http://www.whoi.edu/science/B/people/kamaral/Sound/MammalHits.html
Sound in the Sea[truly amazing!!!]
https://dosits.org/
Intensity of Sound (dB)
I ~ log10
( p² )
Wave amplitude (pressure)
https://youtu.be/WabT1L-nN-E
Video shown in class (whale song) : https://www.youtube.com/watch?v=WabT1L-nN-E
21
Incoming (light) – outgoing (IR) energy flux
Mean annual energy flux at the surface (in W.m-2) and the incoming spectrum (next page)
22
« missing wavelengths » have been absorbed by certain air molecules (0
2 and H
20)
23
Light is absorbed with depth
k=1/δ is the attenuation coefficient, it depends on the wavelength λ
24
FIGURE 3.10
(a) Attenuation coefficient k, as a function of wavelength(m) for clearest ocean water (solid line) and turbid coastal water (dashed line). (b) Relative energy reaching 1, 10, and 50 mdepth for clearest ocean water and reaching 1 and 10 m for turbid coastal waters.
TALLEY Copyright © 2011 Elsevier Inc. All rights reserved
attenuation coefficient =f(λ ; turbidity)
25
26
Marine life impacts sea color
27
https://landsat.visibleearth.nasa.gov/view.php?id=86449
On August 11, 2015, the Operational Land Imager (OLI) on Landsat 8 captured this false-color view of what appears to be a large bloom of cyanobacteria swirling in the Baltic Sea.
Cyanobacteria bloom in the Baltic Sea
28
Questions for biologists Biodiversity at high pressure, cold water? Biodiversity in very salty water (bottom of Red
Sea)? Source of energy for deep ecosystems? What are the colors of abyssal species living in
the dark? Find your question !
