physical oceanography

• 70% covered by water

• 3% of water is freshwater

• 70% of freshwater is found as ice

• Pacific

• Atlanttic

• Indian

• Southern

• Arctic

Fairly large basins of salt water that are connected to the open ocean by one or more small narow channels e.g. North Sea, Baltic Sea

-> those connected by very few channels sometimes are called Mediterranean Seas

connect seperate ocean regions

Ridges that seperate basins

Mean: 3734m

Median: 4093m

Deepest: 11022m Mariana Trench

• Mean depth: 4188m

• Deepest point: Maraiana Trench

• 46% of world ocean area

• 52% of world ocean volume

• Land boundary in the North only broken by Bering Strait (50km deep)

• Mean depth: 3844m

• Deepest point: 9219m

• 23% of world ocean area

• 24% of world ocean volume

• Midatlantic Ridge

• Mean Depth: 3872m

• Max Depth: 7455m

• 20% of global ocean area

• 21% of global Ocean volume

• conneced tp Pacific by Indonesian Throughflow

• Home to the Monsoon system

• Conects Pacific, Atlantic and Indian Ocean

• no meridional boundary

• permanent ice shelves and seasonal sea ice

• 8.8% of global ocean area

• Antarctic circumpolar current

• smallest of the Oceans

• widest continental shelf of all oceans

• nerly surrounded by land, only outlets are the Bering Strait, Davis Strait, Denmark Strait and the Norwegian Sea

• submerged edges of the continents

• consist of massive wedges of sediment eroded from the land and deposited along the continental edge

• can be divided into three parts:

  • shelf

  • slope

  • rise

Shelf:

• <150m water depth

• 1-1000km wide

• most of the oceans fisheries are located here

• bottom gradient: 0.5°

Slope:

• 100m-several km depth

• 10-200km wide

• bottom gradient: 4°-6°

Rise:

• 3000-4000m water depth

• 100-500km wide

• bottom gradient: 0.5°-1°

Structures on the continental slope that are formed by turbidity currents

Area between the continental margins and the mid ocean ridges, icluding features like abyssal plains, abyssal hills, seamounts and deep sea trenches.

Abyssal plains:

• 1-1000km wide

• >3km depth

• Bottom gradient <0

Abyssal Hills:

• 0.1-100km wide

Seamounts: individual under water mountains

• 2-100km wide

Deep Sea Trench:

• 30-100km wide

• continuous submarine mountain ranges that cover one third of the ocean floor

• extends for 60.000km around the earth

• Bottom waters are seperated by oceanic ridges and can leak only through narrow gaps called fracture zones

• Trenches can steer and impact deep boundary currents

• Ocean bottom roughness affects ocean mixing rates

• Seamount chains can e.g. refract tsunami

Altimetry: Echo sounding and seismic reflection give information about topography and sediment layers

and satellite altimetry depending on local mass that result in greater gravitational attraction

• very high surface tension

• very high heat capacity

• very high latent heats of vaporization and fusion

• extremelx good solvent

• densty in the solid phas is less than in the liquid phase att common earth temperatures and pressures

-> 4700J to warm 1kg of water for 1K

• water can store and release large amounts of energy without a major temperature change (90% of human made global warming)

• diurnal temperature differences are much larger over land than over the ocean -> creates circular thermal wind pattern (Monsoon is the seasonal version of this over the Indian Ocean)

Don’t know if tehre is a great effect but ts 335J from ice to water and 2261J from water to vapor

• free moving molecules in the liquid phase are vibrating/moving

• when temperature is reduced below 4°C molecules start forming tetrahedrons that take up more space than the molecules at 4°C -> highest density

• strong jump at freezing point when all molecules are in tetrahedron structure

If this was not the case, lakes in winter would just freeze from the bottom up and all life would eventually disappear

• important for albedo (radiation)

• fresh water export due to brine rejection

• momentum and heat transfer between ocean an atmosphere

Two options with the same result:

1. Rough ocean (Pancake cycle)

• Frazil ice turns into pnacake ice

• Rafting and riding

• Cementation and consolidation

• Sheet ice (rough bottomed)

1. Calm ocean (Congelation growth)

• Frazil ice turns into grease ice

• Nilas

• Rafting

• Congelation ice

• Sheet ice (smooth bottomed)

• O in H2O is weakly negatively charged (attracts cations)

• H in H2O are weakly positively charged (attracts anions)

1. Temperature: Measure of kinetic energy at the molecular level relative to a standard (Celsius scale)

2. Salinity: Measure of the dissolved solids in seawater

3. Pressure: The force exerted by the mass overlying a water particle n the earths gravitational field

amount of mass per unit of volume (kg/m3)

-> determined by temperature, salinity and pressure

-> Temperature relies on pressure (compression leads to an increase in temperature)

-> in situ temperature = temperature of a water parcel at current depth

-> potential temperature = temperature of a water parcel when moved to the surface

absolute Salinity:

mass fraction of dissolved material in seawater

practical Salinity: calculated from the conductivity of seawater (unitless - psu)

highest: Red Sea, Mediterranean, Atlantic subtropical Gyres

lowest: North Pacific ocean

Sources: salt input from weathering through rivers and accumulation in the ocean, (indirectly through evaporation)

Sinks: river runoff, precipitation (highest north of equator, inner tropical convergence zone)

1022-1028kg per m3

Depth interval of constant temperature

-> varies seasonally due to wind mixing and surface heat fluxes

Depth interval of rapidly increasing temperature

-> upper thermocline varies seasonally (seasonal thermocline)

-> lower thermocline is permanent (oceanic thermocline)

Summer:

• Heating produces shallow wind mixed layer and shallow seasonal thermocline

Fall:

• Surface cooling and more storms cause deeper wind mixed layers and shrinking of the shallow thermocline

Winter:

• Further cooling and wind increase wind mixed layer and eliminates the shallow thermocline

Spring:

• Thermocline reforms due to heat gain and cycle starts again

-> deep thermocline remains all year

Thermocline: depth interval of rapidly increasing temperature

Halocline: depth interval of rapidly increasing salinity

Pycnocline: depth interval of rapidly increasing density

1Hz-10MHz with wave lengths of 1500m-0.15mm

• compressional waves

• longitudinal polarized (displacement parallel to wave vector)

• dispersionless (phase speed ~ independent of frequency)

air: 341m/s

water 1480m/s

-> only a small amount of sound energy starting in one medium can penetrate into the oher

Depends on temperature, salinity and pressure

-> salinity has barely any effect on sound speed

-> the deeper you go the faster the sound speed

-> the warmer it is the faster the sound speed

-> temperature dominates in the upper ocean while pressure dominates in the lower ocean

• along concentric circles from source

• distance between constant phase lines depends on sound speed

Snell’s Law: when going from one region to another the direction will change by the time of entering the second region

• Gamma 2 is larger than Gamma 1

• sin Gamma 2 has a higher value

• C2 must be larger

Rule: sound waves are refracted towards tthe region with lower sound speed

• sound depends strongly on water ttemperatures (can be used to determine large scale average temperature changes

• changes in runtime between the scoustc instruments are caused by changes in sound speed

• transmit sound pulses at a fixed frequency

• Sound is scattered at small particles that are advected by ocean currents

• Depending on the movement of the reflecting feature, the frequency of the sound changes (Doppler effect)

• Instrument listens to the Doppler shifted reflected/backscattered sound

• Reflector movement and thus ocean current can be determined

Reflected: energy is returned unchanged (at surface)

Absorbed: energy is given to the object for atomic or molecular reactions (below surface)

Scattered: reflection with random direction (e.g. due to particles) (below surface)

Transmitted: direction of propagation changes

Emitted: once absorbed energy can be emitted (usually at longer wave lengths

Net reduction in radiance, irradiance, or intensity resulting from both absorption and scattering

Seawater absorbs red and yellow light and the remaining blue light is reflected back to our eye.

When there is a lot of suspended material in the water the colour can change (e.g. green due to absorbtion of blue and red by chlorophyll or brown due to CDOM)

-> Coloured Dssolved Organic Matter

Results of tannins released from decaying detritus

Can change colour of water in estuaries and lakes

Bottom typically defined as depth where energy has fallen to 1% of value immediately below surface

• classification based on water clarity as quantified by diffuse attenuation coefficient KEd

• Open Ocean: type I, IA, IB, II, II (clear -> turbid)

• Coastal water: type 1, 2, 3, 4, 5, 6, 7, 8, 9 (clear -> turbid)

• based on transmittance along 1m of seawater

Input:

• precipitation onto the surface

• river input

• melting ice (icebergs and sea ice)

Output

• evaporation from the surface

• sea ice formation

• movement of water within the ocean

Transport: Stuff per time

• volume transport -> m3/sec (10^6m3/sec = 1Sv)

• salt transport -> kg/sec

• heat transport -> J/sec

Flux: Transport per unit area (stuff per time per area)

Budget: Transport in and out of a closed volume

-> evaporation exceeds precipitation plus river runoff

-> negative: Mediterranean sea (leads to outflow of high salinity water and inflow of low salinity water from the North Atlantic)

-> positive: Black Sea (net gain of fresh water from precipittation and runoff)

High

• inter tropical convergence zone (ITCZ) north of the equator

• indopacific warmpool regions (western part of the tropical Pacific and eastern partt of the tropical Indian Ocean)

  -> where ascending branch of the atmospheric walker circulation is found

• Northwestern Pacific and Atlantic above western boundary currents

Low

• eastern subtropical regions where descending branch of headley circulation is found

Solar radiation: short wave length -> more energy

Terrestrial radiation: longer wave length -> less energy

Water: 6%

Ice: 50%

Snow: 90%

Clouds: 40-90%

forest: 5-20%