Transcript Multidecadal Meridional Overturning Circulation

Inter-annual to decadal climate prediction
Mojib Latif, Leibniz Institute of Marine Sciences at Kiel University
Outline
1. Some general remarks
2. Inter-annual predictability
3. Decadal predictability
4. Limitations
The last three decades
annual global SAT
Uncertainties in climate change
projections
annual global SAT, derived from CMIP3 models
internal variability
scenario
model
Hawkins and Sutton 2009
Uncertainty due to internal variability
increases at regional scales
internal variability
internal variability
Hawkins and Sutton 2009
Unpredictable external factors enhance the uncertainty
Potential predictability at inter-annual
and decadal time scales
Outline
1. Some general remarks
2. Inter-annual predictability
3. Decadal predictability
4. Limitations
El Niño/Southern Oscillation
The role of air-sea interactions
and upper ocean heat content
A simple theoretical concept has been developed
The ocean observing system
Three days (24-26 March 2010) of real-time in situ data from moorings (red
squares), Argo floats (inverted yellow triangles), drifters (blue circles), shore
and bottom stations (blue triangles), and ships (green symbols).
The TOGA TAO array, the basis for ENSO prediction
El Niño prediction, November
starts predicting winter (DJF)
r = 0.96
NAO prediction, November starts
predicting winter (DJF)
r = 0.27
What’s next?
Outline
1. Some general remarks
2. Inter-annual predictability
3. Decadal predictability
4. Limitations
Multidecadal climate variability
Is some of the multidecadal variability in NH-SAT linked
to MOC variations, and if so, are they predictable?
Societal relevance of multidecadal
variability
Latif et al. 2009
The North Atlantic Oscillation (NAO)
NAO-related SAT pattern (°C),
+1σ
The NAO can affect Labrador
Sea convection
The NAOI spectrum is almost white,
but there is multidecadal variability
MOC may respond to the multidecadal changes
Forced ocean model MOC and
Northern Hemisphere temperature
ORCA (0.5°) forced by
“observations”, courtesy F. Alvarez and
A. Biastoch
MOC may have contributed to the accelerated NH
warming in the recent decades
MOC since 1950 in different analyses
Jin Ba, IFM-GEOMAR
The analyses are all over the place
Initialized forecasts for the next
decades are highly uncertain
Outline
1. Some general remarks
2. Inter-annual predictability
3. Decadal predictability
4. Limitations
Climate models suffer from
large biases
IPCC 2007
Errors can amount to several degrees in
certain regions
We lack understanding of the mechanisms
underlying decadal variability
NAO tends to
lead MOC
MOC tends to
lead SST
There is a large spread in the model results,
which was expected given the large biases.
Convection sites, for instance, are misplaced
in several models.
Do we understand abrupt
climate change?
Summary
•A predictability potential exists at inter-annual and decadal time
scales
•Inter-annual predictability is restricted mostly to the Tropics,
decadal predictability to mid and high latitudes
•Inter-annual prediction is much more advanced
•This is mostly due to a suitable observing system
•The (inter-annual) skill, however, is mostly limited to the Tropics
•Decadal predictability seems to exist mostly in the mid and high
latitudes
•It is likely related to variations of the AMOC (in the Atlantic)
•We are, however, strongly limited by the lack of data and our
understanding of the physical mechanisms, and by rather large
model biases
Thank you for your
attention