properties of ocean water Flashcards
what are the properties of water? (5)
Transparency = clarity; clearness
- Light can reach photosynthetic organisms e.g.
phytoplankton & seaweeds
- Organisms can see through water
Cohesion and adhesion = water sticks to itself and to other materials - Surface tension - Organisms can ‘walk’ on water e.g. sea slugs, water strider
Solvent (almost universal – most substances will
dissolve in water)
- Salinity of oceans
- Dissolved nutrients & gases
High specific heat capacity (a lot of energy is
required to change the temp. / state of water)
- Relatively little variation in ocean temperature
- Ocean is involved in moderation of climate
- Ocean can store more heat than land surfaces
Density of ice (solid water) is less than liquid
water
- Ice floats and provides protection for aquatic
organisms living under the ice
- Oceans (and lakes) will not freeze solid
neutral ph
low viscosity
- Water flows easily
- Organisms can swim through water
at what temperature the water is 1.00 dense?
3.98
Where on earth is the water?
Atmosphere Ocean Ice caps Land plants Animals Soil Rocks (igneous) Bodies of freshwater
how does water transformation influence the climate?
When water evaporates, it takes energy
from the surroundings
When water condenses, it adds heat energy
to the environment
how was the ocean created?
Off-gassing of igneous rocks via volcanoes,
followed by condensation, precipitation and
accumulation of liquid water
Comets (rocks & ice) brought water to earth
what were the conditions of early earth?
4.6 billion years old - red, hot snowball
Early atmosphere formed by volcanism
Composition: mostly CO2, with little or no
oxygen
Also, smaller proportions of water vapour,
ammonia and methane
Evidence from ice cores
what’s seawater and what does it contain?
A solution of dissolved solids and gases
One liter (1000 g) of seawater contains about 35 g of dissolved materials
35 parts per thousand (ppt) or 3.5 %
which ions are in seawater?
Chloride (Cl-) 55.04
Sodium (Na+) 30.61
Sulphate (SO42- 7.68
Magnesium (Mg2+) 3.69
Calcium (Ca2+) 1.16
Potassium (K+)
why is the ocean salty?
Inputs / sources of salt:
Freshwater run-off does contain ions from the
erosion of rocks / soil
Volcanism / hydrothermal vents / uplift
Input from the atmosphere
Outputs from the ocean to atmosphere and
into ocean sediments & mantle
Transformations within the ocean
Different residence times of ions
Why are the proportions of ions in freshwater and in seawater different?
Oceans are not just passive receptacles of water, there is a nutrient process
Some organisms use these ions and nutrients for themselves
what is the residence time of ions?
average amount of time that an ion spends in the ocean:
- Most abundant ions, long residence time
- Least abundant ions, short residence time
how to measure seawater temperature?
Thermometer – alcohol or mercury Reversing thermometer (depth) Bathythermograph / XBT Thermistor - Temperature probe & meter - CTD Acoustic tomography / sound (ATOC) Satellite remote sensing (SST) Ocean surface topography
how to measure seawater salinity?
Evaporation Chloride titration Conductivity - Salinity probe & meter - CTD Refractometer Satellite remote sensing (SSS)
how to measure seawater ph?
Universal indicator / pH paper / litmus paper
Chemical titration
pH probe & meter
Ocean pH sensor
how to measure seawater oxygen?
Oxygen probe & meter
Colorimetric method
Winkler titration: a sample bottle is filled completely with water(no air). the dissolved oxygen than is fixed by creating an acid compound through the addition of reagents which will be eventually titrated with a neutralizing compound that will change the color of water=> endpoint coincides with the amount of dissolved oxygen
what’s pycnocline?
a layer in an ocean or other body of water in which water density increases rapidly with depth.
what’s thermocline?
A layer in a large body of fluid in which temperature changes more drastically with depth than it does in the layers above or below
what’s halocline?
, vertical zone in the oceanic water column in which salinity changes rapidly with depth
how does the pycnocline act like a barrier to water circulation and organism movement?
Warmer, less salty upper layer is separated from colder, more salty lower layer
Low-density fluid floats on top of high-density fluid
System is very stable – requires a great deal of energy to overcome the stability
what are three most abundant gases in seawater?
nitrogen (N2), oxygen (O2) and carbon dioxide
CO2
what are the chemical processes affecting dissolved gases in seawater?
Oxygen produced by photosynthesis and
consumed via respiration
Carbon dioxide is consumed by photosynthesis and produced by respiration and can modify
solubility of gases in water
The amount of gas that can be dissolved in water depends on the temperature of the water. More gas can dissolve in cold water than in hot water.
what’s the mixed layer?
the above layer with lots of oxygen through diffusion from atmosphere and photosynthesis
Layer of water that exists between waters surface and the clines (steep gradients in abiotic factors)
Water temp and salinity remain constant in this mixed layer
Results from turbulence caused by wind and wave action
There is a deepening of the mixed layer with increasing wind strength and duration
Varies between 25-200m in depth
what’s oxygen minimum layer and what are its characteristics?
high rate of O2
consumption by bacteria decomposers (of sinking
organic material e.g. phytoplankton)
Deep ocean has reasonable amount of oxygen
because rate of O2 consumption is minimal and
thermohaline circulation
what’s pH?
a measure of how acidic the water is
what’s the two-layered ocean?
mixed layer and oxygen minimum layer
ocean acidification
Decrease in pH of oceans as a result of their uptake of anthropogenic carbon dioxide from the atmosphere
how the transmission of light, sound
and heat through the ocean?
Near the equator, the sun’s rays strike the
ocean almost perpendicular to the ocean’s
surface – direct!
Near the poles, the sun’s rays strike the ocean
at an angle, rather than directly
More energy penetrates the surface of the water
at the equator than at the poles
how the transmission of light through the ocean happen?
Near the equator, the sun’s rays strike the
ocean almost perpendicular to the ocean’s
surface – direct!
Near the poles, the sun’s rays strike the ocean
at an angle, rather than directly
More energy penetrates the surface of the water
at the equator than at the poles
how does light manifest in the ocean?
Not affected by mixing & there is no cline of light.
Light decreases with depth because it is absorbed by sediment particles and plankton
how does the transmission of sound through the ocean happen?
Sound waves travel faster in water than in air
- In air at 18oC, the speed of sound is ~341 m/s
- In salt water at 18oC, the speed of sound is ~1,524 m/s
Long wavelength sounds travel further than
short wavelength sounds
Low frequency, long wavelengths
how can sound be used?
Sound can be used to measure ocean
temperature, salinity, depth, plankton (ZAP)
and to map the ocean floor ( A sonar device sends out a burst of ultrasound waves that travel through the water and strike the ocean floor or an object, causing them to reflect. The sonar device detects the reflected waves)
