ocean observation and thermohaline circulation

Question 1

what is the development of oceanography?

Answer 1

knowing where you are, latitude and longitude.

Question 2

what is longitude?

Answer 2

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

Question 3

what are the important latitudes?

Answer 3

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

Question 4

how do you determine latitudes?

Answer 4

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

Question 5

what is latitude from sextant?

Answer 5

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

Question 6

what is the line of longitude?

Answer 6

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

Question 7

what was the first modern study of oceans?

Answer 7

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.

Question 8

how do you sample water columns?

Answer 8

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)

Question 9

what measures water columns?

Answer 9

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.

Question 10

what are the observations made from satellite sensing?

Answer 10

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.

Question 11

what is a geostationary orbit?

Answer 11

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

Question 12

what is a polar orbit?

Answer 12

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

Question 13

what is Sverdrup?

Answer 13

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

Question 14

how do density differences affect water masses?

Answer 14

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.

Question 15

what determines seawater density?

Answer 15

Seawater density is determined primarily by temperature and salinity.

Question 16

what is potential temperature?

Answer 16

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.

Question 17

what is potential density?

Answer 17

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

Question 18

what is the circulation in marginal seas and basins?

Answer 18

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

Question 19

why is circulation important?

Answer 19

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

Question 20

what does circulation do?

Answer 20

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

Question 21

what are high latitude processes?

Answer 21

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

Question 22

what results in sinking?

Answer 22

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

Question 23

what forms a chimney?

Answer 23

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

Question 24

what are the 4 stages of ocean deep convection?

Answer 24

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

Question 25

why is the Mediterranean important?

Answer 25

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

Question 26

what is the importance of Agulhas?

Answer 26

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.

Question 27

what monitors thermohaline circulation?

Answer 27

Rapid SMOC monitoring, Atlantic meridional overturning circulation.

Question 28

what happened in 2002?

Answer 28

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.

Question 29

what is the record for gulf stream time series?

Answer 29

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

Question 30

what is the MOC reduction?

Answer 30

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.

Question 31

what is RAPID?

Answer 31

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

Question 32

what is decadal?

Answer 32

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

Question 33

what is the continental slope?

Answer 33

Continental slope: descends into the depths of 4 km.

Question 34

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

Answer 34

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.

Question 35

what is the continental rise?

Answer 35

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

Question 36

what is the active continental margin?

Answer 36

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

Question 37

why are broa continental shelves not plate boundaries?

Answer 37

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