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Part I Ocean and Climate (heat transport and storage) PowerPoint PPT Presentation


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Ocean circulation Arnaud Czaja 1. Ocean and Climate 2. Key observations 3. Mechanisms of ocean-atmosphere coupling. Part I Ocean and Climate (heat transport and storage). Net energy loss at top-of-the atmosphere. =. +. Poleward energy transport. Ha. Ho.

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Part I Ocean and Climate (heat transport and storage)

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Part i ocean and climate heat transport and storage

Ocean circulationArnaud Czaja1. Ocean and Climate2. Key observations3. Mechanisms of ocean-atmosphere coupling


Part i ocean and climate heat transport and storage

Part IOcean and Climate(heat transport and storage)


Part i ocean and climate heat transport and storage

Net energy loss at

top-of-the atmosphere

=

+

Poleward energy

transport

Ha

Ho

Imbalance between and

= energy (heat) storage


Poleward heat transport and storage are small

Poleward heat transport and storage are small…

Energy exchanged at

top-of-atmosphere :

Planetary albedo

Solar constant


Seasonal heat storage

SeasonalHeat storage

Q5


Bjerknes 1964 monograph data from sverdrup 1957 houghton 1954

Heat transport: a long history of measurements…

Bjerknes’ (1964) monograph. Data from Sverdrup (1957) & Houghton (1954)

Ha+Ho

Ha

Northward heat transport

Ho

Equator

Pole


Part i ocean and climate heat transport and storage

Ha+Ho

Ha

Northward heat transport

Ho

70N

50N

10N

30N

Vonder Haar & Oort, JPO 1973.

GERBE

approved!


Part i ocean and climate heat transport and storage

NB: 1PW = 10^15 W

“Across the same latitude, Ha is 1.7PW. The ocean

therefore can be considered to be more important

than the atmosphere at this latitude in maintaining

the Earth’s budget”.

Hall & Bryden, 1982; Bryden et al., 1991.


Part i ocean and climate heat transport and storage

GERBE

approved!

(ask more to Chris D.!)

Trenberth & Caron, 2001


Part i ocean and climate heat transport and storage

GERBE

approved!

Ha+Ho

Ho

Ha

Wunsch, JCl. 2005.


Part i ocean and climate heat transport and storage

Ganachaud & Wunsch, 2003


Sometimes effects of heat storage and transport are hard to disentangle

Sometimes effects of heat storage and transport are hard to disentangle

  • Is the Gulf Stream responsible for “mild” European winters?


Part i ocean and climate heat transport and storage

WARM!

COLD!

Eddy surface air

temperature from

NCAR reanalysis

(January, CI=3K)

“Every West wind that blows crosses the Gulf Stream on its way to Europe,

and carries with it a portion of this heat to temper there the Northern winds

of winter. It is the influence of this stream upon climate that makes Erin the

“Emerald Isle of the Sea”, and that clothes the shores of Albion in evergreen

robes; while in the same latitude, on this side, the coasts of Labrador are fast

bound in fetters of ice.”

Maury, 1855.

Lieutenant Maury

“The Pathfinder of the Seas”


Model set up seager et al 2002

Model set-up (Seager et al., 2002)

  • Full Atmospheric model

  • Ocean only represented as a motionless “slab” of 50m thickness, with a specified “q-flux” to represent the transport of energy by ocean currents

Atmosphere


Part i ocean and climate heat transport and storage

Q3

Seager et al.

(2002)


Heat storage and climate change

Heat storage and Climate change

The surface warming due to +4Wm-2 (anthropogenic

forcing) is not limited to the mixed layer…

How thick is the layer is a key question to answer to predict accurately the timescale of the warming.

Ho = 50m

Ho = 150m

Ho = 500m

NB: You are welcome to

download and run the model :

http://sp.ph.ic.ac.uk/~arnaud


Ensemble mean model results from the ipcc ar4 report

Q1

Ensemble mean model resultsfrom the IPCC-AR4 report


Strength of ocean overturning at 30n a1b scenario constant after yr2100

Strength of ocean overturning at 30N (A1B Scenario + constant after yr2100)

Q4


Part ii some key oceanic observations

Part IISome key oceanic observations


Part i ocean and climate heat transport and storage

World Ocean Atlas surface temperature

ºC


Part i ocean and climate heat transport and storage

Thermocline


Part i ocean and climate heat transport and storage

World Ocean Atlas Salinity (0-500m)

psu


The great oceanic conveyor belt

The “great oceanic conveyor belt”


The ocean is conservative below the surface 100m layer

The ocean is conservative below the surface (≈100m) layer

  • Temperature No heat exchange, only pressure effects.

  • Salinity. No phase change in the range of observed concentration.


Conservative nature of the ocean

Salinity on 1027.6 kg/m3 surface

Conservative nature of the ocean

Spatial variations of

temperature and salinity

are similar on scales from

several hundreds of kms to a few kms.

10km

2km

50km

Ferrari & Polzin (2005)


Part i ocean and climate heat transport and storage

Matsumoto, JGR 2007


Circulation scheme

“Circulation” scheme


Part i ocean and climate heat transport and storage

Q6

Broecker, 2005

NB: 1 Amazon River ≈ 0.2 Million m3/s


Circulation scheme1

“Circulation” scheme

Two “sources” of deep water:

NADW: North Atlantic

Deep Water

AABW: Antarctic Bottom

Water

Williams & Follows (2009)


In situ velocity measurements

In – situ velocity measurements

Amplitude of

time variability

Location of “long”

(~2yr) currentmeters

Depth

NB: Energy at period < 1 day

was removed

From Wunsch (1997, 1999)


Part i ocean and climate heat transport and storage

Moorings in the North Atlantic interior

(28N, 70W = MODE)

(ask more to Ute and Chris. O.!)

1 yr

NB: Same velocity vectors but rotated

Schmitz (1989)


Part i ocean and climate heat transport and storage

Direct ship

observations

NB: 1m/s = 3.6kmh = 2.2mph = 1.9 knot


Surface currents measured from space

Surface currents measured from Space

“Geostrophic balance”

Standard deviation of sea surface height

Time mean sea surface height


Momentum balance

Momentum balance

Rotation

rate f/2

East to west

acceleration

f V

East to west

deceleration

up

North

NB: f = 2 Ω sinθ

East


Geostrophic balance

Geostrophic balance!

Rotation

rate f/2

High

Pressure

Low

Pressure

East to west

acceleration

f V

East to west

deceleration

up

North

East


10 yr average sea surface height deviation from geoid

10-yr average sea surface height deviation from geoid

Subtropical gyres


10 yr average sea surface height deviation from geoid1

10-yr average sea surface height deviation from geoid

Subpolar gyres

Antarctic Circumpolar

Current


Argo floats since yr 2000

ARGO floats (since yr 2000)

T/S/P profiles every 10 days

Coverage

by lifetime

Coverage

by depths


Part i ocean and climate heat transport and storage

All in-situ observations can be interpolated dynamically using numerical ocean models

Overturning

Streamfunction

(Atlantic only)

From Wunsch (2000)


Part i ocean and climate heat transport and storage

RAPID – WATCH array at 26N

Q2


Part i ocean and climate heat transport and storage

RAPID – WATCH array at 26N

14 millions £


The movie

The movie…


Friday s session

Friday’s session


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