ocean observation and thermohaline circulation Flashcards Preview

1 SOES1008 earth and ocean systems > ocean observation and thermohaline circulation > Flashcards

Flashcards in ocean observation and thermohaline circulation Deck (37)
Loading flashcards...
1
Q

what is the development of oceanography?

A

knowing where you are, latitude and longitude.

2
Q

what is longitude?

A

Longitude is upwards scale of lines, latitude is the horizontal scale of lines.

3
Q

what are the important latitudes?

A

Important latitudes- summer solstice 21st june and the winter solstice, dec 21st.

4
Q

how do you determine latitudes?

A

Determining latitude: observations enhanced by astrolabe from 160 B.C- used also for navigation.

5
Q

what is latitude from sextant?

A

Latitude from sextant: angles used to calculate the latitude. Alpha is the altitude of the sun at moon measured with the sextant. Delta is the declination of the sun, obtained from nautical almanac

6
Q

what is the line of longitude?

A

Knowing where you are in longitude is harder, as you need to know precise time differences from a reference, line of longitude.

7
Q

what was the first modern study of oceans?

A

First modern scientific study of the oceans HMS challenger, which measured surface water temperatures, salinity and currents. Measured bottom depth by sounding, dredged sea floor rocks and collected biota, in 1872-76.

8
Q

how do you sample water columns?

A
Sampling the water column- the Nansen bottle. Messenger trips release, second messenger flips it, reversing thermometer temperatures of the depth at which the bottle was filled. 
CTD probes (conductivity, temperature, depth)
9
Q

what measures water columns?

A

Autonomous Argo floats, regulate buoyancy and transmit CTD data via satellite. Argos floats, there are a lot of the, massive coverage in the oceans.
Observation from ROVs and AUVs with sensor packs.

10
Q

what are the observations made from satellite sensing?

A

Observations from space-satellite remote sensing, examples of parameters measured, sea surface temperature IR scanning, ocean colour/optics visible, sea surface height and currents in radar, and surface wind stress of surface roughness and microwave.

11
Q

what is a geostationary orbit?

A

Geostationary orbit-GEO, 36,000km altitude, stays over the same location, can document evolving systems, high temporal resolution, no polar coverage

12
Q

what is a polar orbit?

A

Polar orbit- low earth orbit LEO, travels nearly over the poles sees almost the whole earth regularly, lower temporal resolution.

13
Q

what is Sverdrup?

A

Use the “Sverdrup” Sv.
Total global input of fresh water from rivers to the oceans is 1.3 Sverdrup.
The water transport in the gulf stream gradually increases from 30 Sv in the Florida current to a maximum of 150 Sv south of newfoundland

14
Q

how do density differences affect water masses?

A

Density differences cause water masses to sink or rise to the appropriate density and them move outwards to flow between lower density water above and higher density water below.

15
Q

what determines seawater density?

A

Seawater density is determined primarily by temperature and salinity.

16
Q

what is potential temperature?

A

Potential temperature: is defined as the temperature of a parcel of water at sea surface after it has been raised adiabatically from some depth in the ocean. Raising the parcel adiabatically means that it is raised in an insulated container so it doesn’t exchange heat with its surroundings.

17
Q

what is potential density?

A

Potential density- is the density of a parcel of water would have if it were raised adiabatically to the surface without change in salinity.

18
Q

what is the circulation in marginal seas and basins?

A

Circulation in marginal seas and basins: general patterns of circulation in seas and oceans basins often refer to analogies with estuaries.

19
Q

why is circulation important?

A

Why is it important? It regulates our climate through heat transport to high latitude. Without it, there would be ice everywhere.

20
Q

what does circulation do?

A

It initiates the sinking of surface waters, most likely to occur where ow temperatures occur at high latitudes.

21
Q

what are high latitude processes?

A

High latitude processes- most likely to occur where low temperatures occur at high latitudes.

22
Q

what results in sinking?

A

Cooling in open ocean polynyas also results in sinking, but this sinking is driven by temperature so deep waters has different character.

23
Q

what forms a chimney?

A

Initial cooling and loss of stratification forms a chimney where deep convection occurs.

24
Q

what are the 4 stages of ocean deep convection?

A

Phases of open ocean deep convection: preconditioning, violent mixing, restratification 1, and restratification 2.

25
Q

why is the Mediterranean important?

A

Mediterranean is very important; deep convection, caused by cooling seasonal winds. Fortuitous observation of stimulation of deep sea ecosystems.

26
Q

what is the importance of Agulhas?

A

Importance of Agulhas “leakage” for return of warm saline waters: Agulhas rings important for transfer of warm saline waters, but as they are anticyclonic, they are centres of downwelling, forming warm core rings, with lower productivity.

27
Q

what monitors thermohaline circulation?

A

Rapid SMOC monitoring, Atlantic meridional overturning circulation.

28
Q

what happened in 2002?

A

2002- NOCS scientists proposed to continuously monitor the automatic circulation. RAPID array project, estimating the trans-basin overturning MOC, continuously over 12 hours.
Calculating MOC- EK(t) + GS(t) +MO(t)=0.

29
Q

what is the record for gulf stream time series?

A

Gulf stream transport time series from electromagnetic cable.
Continuous record between 1982 and present.

30
Q

what is the MOC reduction?

A

Structure of deep western boundary current
The mean- is around 18 Sv expectation- the atlantic MOC is 18, changes on the order of Sv are large, but slowdown of MOC from hydrology. The MOC reduciton increased an aliasing of the seaosnla cycle.

31
Q

what is RAPID?

A

RAPID- mean and seasonal time scales, expectiation, the mean is 18 small variability. Decine of 30% seen since 1957.

32
Q

what is decadal?

A

Decadal- climate model forecasts lead us to expect a decline of the MOC of 25 % over the next 100 years.

33
Q

what is the continental slope?

A

Continental slope: descends into the depths of 4 km.

34
Q

how does the oceanic and continental lithosphere different in thickness and how does this create the ocean?

A

Oceanic lithosphere and continental lithosphere differ in terms of composition and thickness- hence the ocean exists. Continental shelf: shallow portion of the ocean in which water depth doesnt exceed 500 m. Ocean floor slopes seawards, an almost imperceptible amount.

35
Q

what is the continental rise?

A

Continental rise: the angle decreases, you find yourself about a vast plain- the abyssal plain.

36
Q

what is the active continental margin?

A

Active continental margin: margin that coincides with a plate boundary and thus hosts many earthquakes.
Submarine canyons- dissect continental shelves and slopes.

37
Q

why are broa continental shelves not plate boundaries?

A

Broad continental shelves form along passive continental margins, that are not plate boundaries and thus host few earthquakes.