Intermediate and deep ocean circulation

Question 1

Average depth of the ocean

Answer 1

3.5-3.8km

Question 2

Low latitudes vs high latitudes

Answer 2

Net warmingin low latitudes and net cooling in high latitudes

Question 3

Mid- latitiude waters

Answer 3

Warmer and more saline than interior waters

Question 4

Weak thermocline

Answer 4

High intrinsic density= cooled waters sink
–> Common in high northern latitudes

Question 5

Halocline

Answer 5

Vertical zone in water where there is a rapid change in salinity

Question 5

Ocean surface waters mixing

Answer 5

Wind-driven waves and Ekman spiral cause mixing meaning T and S change little with depth

Question 6

Flow in surface waters

Answer 6

Dominated by wind stress

Question 7

Equatorial upper water- equatorial winds

Answer 7

Trade winds blow west in the tropics–> warm surface water piles up on W of ocean basins–. creates strong eastward currents –> Coriolis deflects moving water

Question 8

Thermocline- equatorial regions

Answer 8

DEEP thermocline - WESTERN side
SHALLOW thermocline- EASTERN side

Question 9

Central Open waters

Answer 9

While surface water sinks in subtropical gyre centers, Ekman transport driven by the gyre’s wind system piles up saltier water in mid-latitudes due to convergence.

Question 10

Seasonal effects on mixing

Answer 10

In mid-latitudes, warming produces a warm and saline layer of surface water which is thickened and mixed but remains buoyant. In winter, water cools and sinks–> causes vigorous mixing

Question 11

Central Ocean Water (COW) boundaries

Answer 11

COW= warmer and saltier therefore stays distinct from surrounding water masses down to 1,000 meters. Can be separated by underwater features like island chains. The Coriolis effect and wind patterns create separate bodies of COW in the N and S Hemispheres.

Question 12

Western NACW

Answer 12

–> Forms by sinking and mixing of surface water in the Sargasso Sea gyre; salinity 35.5-36.5 PSU; temp 7-20C
–> SACW; 5-18C, 34.3-35.8 PSU

Question 13

Arctic and Antarctic Upper Water

Answer 13

Direct wind drag causes convergence and piling up surface waters around polar front

Question 14

Temperature contrast between surface and deep water

Answer 14

= small in high latitudes so the distinction between Surface, Upper and Intermediate
–> Arctic and Antarctic Upper Waters = surface occurrence of the corresponding Intermediate Waters

Question 15

Intermediate water masses

Answer 15

Denser than Upper and Surface Water but less dense than Deep Water
–> Intermediate density due to reduced salinity or high temp

Question 16

Antarctic Intermediate Water (AAIW)- formation

Answer 16

Dilution of cool deep water by icebergs just to the north of the south polar front

Question 17

Features of AAIW

Answer 17

Low temperature 3-5C makes water contract ad sink but low salinity (34.3%) makes it float above dense saline water

Question 18

Depths of AAIW

Answer 18

500-900m/ 700-1200m

Question 19

Features Mediterranean Water

Answer 19

• High salinity 35-36.2 offset by high temp (8-10C)–> Intermediate density

Question 20

Another name for Pacific Subarctic intermediate water=

Answer 20

North Pacific Intermediate Water (NIPW)

Question 21

North Pacific vs North Atlantic

Answer 21

Less evaporation and more precipitation therefore less saline- drops below 32%

Question 22

Features of NPIW

Answer 22

Cool- 3-8C and low salinities 34-34.5

Question 23

NADW - North Atlantic Deep Water (NADW)

Answer 23

Generated by the sinking of surface waters in high latitudes generating cold, highly saline water

Question 24

2 principle original deep water masses

Answer 24

North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW)

Question 25

Formation of NADW

Answer 25

Formed by winter cooling of high salinity surface water in N Atlantic

Question 26

Features of NADW

Answer 26

Moderately cold:2-5C Highly Saline (34.9%)

Question 27

Formation of AABW

Answer 27

Formed by sea ice freezing and is the most widespread ocean water type

Question 28

Features of AABW

Answer 28

Very cold :-2 to 1 C Moderately high salinity (34.6-34.7%)

Question 29

Density AABW vs NADW

Answer 29

AABW is slightly denser than NADW

Question 30

NADW is a mixture of water masses from 3 main areas:

Answer 30

- Norwegian and Greenland Seas - Central Arctic Ocean

Question 31

North Atlantic Drift

Answer 31

Warm, salty water from Gulf stream and N Atlantic Gyre reach Norwegian sea as the North Atlantic Drift= key source of salinity in NADW

Question 32

Winter cooling NADW

Answer 32

Strong cold winder winds in Norwegian Sea cause intense cooling and mixing of the surface water with underlying colder and less saline waters

Question 33

LNADW- lower North Atlantic Deep Water

Answer 33

= v.dense- formed in Norwegian sea. Temp=higher than AABW

Question 34

UNADW- Upper North Atlantic Deep Water

Answer 34

- Formed in the Labrador Sea through winter cooling - lower density than LNADW

Question 35

Sea ice

Answer 35

Forms from salt water but the ice crystal are of pure water, leaving the salt behind in the un-frozen residual sea water.

Question 36

Why doesn't salt in ocean freeze?

Answer 36

Salt ions interfere with the ability of water molecules to form ice crystal lattice structure

Question 37

Origin of ice at sea:

Answer 37

1. Continental ice sheet that has slip off but flows coherently 2. Icebergs- float independently 3. Salt water freezing

Question 38

Polynya

Answer 38

Continuing open water in a region of sea ice e.g. Weddell Sea

Question 39

Where do submarine waterfalls occur?

Answer 39

Middle of Atlantic Ocean

Question 40

Order of Atlantic deep ocean circulation N-S

Answer 40

Lowest density --> Highest density= 1. Mediterranean overflow water (MOW) 2. Antarctic Intermediate water (AAIW) 3. North Atlantic Deep Water (NADW) 4. Antarctic Bottom Water (AABW)

Question 41

Journey of NADW

Answer 41

NADW forms in two basins in the North Atlantic, separated by ridges. It spills southward over sills, with some denser Norwegian Sea water traveling through a specific zone. It travels south along the west side of the Atlantic, then overrides colder bottom water around 20°N. Continuing south, NADW becomes a layer between deeper and shallower water masses. Eventually, it mixes with them to form a new water type that feeds into the formation of another important layer and gets carried around the globe by a major current.

Question 42

AABW - journey

Answer 42

AABW (cold)- cannot cross the MOR in the S Atlantic Bottom Water in Nordic seas cannoAAt cross the Shetlands-Iceland Ridge

Question 43

AABW flow patterns

Answer 43

AABW takes a complex path through the South Atlantic. The Weddell Sea funnels AABW into the Argentine Basin. Some "Common Water" from the ACC also enters. Underwater ridges block direct flow from the ACC into another basin (Angolan). AABW mainly travels north, exiting the Argentine Basin through a gap to reach western North Atlantic basins. A smaller portion goes east, warming slightly as it crosses a ridge to reach the Guinea Basin. Northward flow from there is limited, but some AABW spills south. Minor amounts enter eastern North Atlantic basins through fracture zones.

Question 44

Pacific- Indian Ocean Common Water (PIOCW)

Answer 44

Mixture of AABW and NADW

Question 45

Features of PIOCW

Answer 45

salinity- 34.7% temperature : 1.5C