Post on 28-Jan-2016
Climate Forecasting Unit
Arctic Sea Ice Predictability and Prediction on Seasonal-to-
Decadal Timescale
Virginie Guemas, Edward Blanchard-Wrigglesworth, Matthieu Chevallier, Michel Déqué, Francisco Doblas-Reyes, Neven S Fuckar, Francois Massonnet, Danila
Volpi, David Salas y Mélia
Climate Forecasting Unit
I - Arctic sea ice predictability sourcesPersistence
Sea Ice Thickness Sea Ice Thickness
Guemas et al (2014) QJRMS
Climate Forecasting Unit
I - Arctic sea ice predictability sources
Chevallier and Salas-Melia (2012) Journal of Climate
Ice thickness preconditioning
Thick ice = best predictor of September extent, thin ice good predictor for March
extent
Chevallier and Salas y Mélia, JCLIM, 2012
Total volume
Total area
Area of ice h > 0.9m
Area of ice h > 1.5m Area of ice h < 1.5m
Total volume
Total area
Area of ice h < 0.9m
Climate Forecasting Unit
I - Arctic sea ice predictability sourcesAdvection
Guemas et al (2014) QJRMS
Climate Forecasting Unit
I - Arctic sea ice predictability sourcesOcean heat transport
Guemas et al (2014) QJRMS
Correlation detrended annual-mean ORAS4 60N heat transport and sea ice concentrationAtlantic OHT lag -3 Pacific OHT lag -3
-0.8 -0.6 -0.4 -0.2 0.2 0.4 0.6 0.8
Climate Forecasting Unit
I - Arctic sea ice predictability sourcesReemergence
Blanchard-Wrigglesworth al (2011) Journal of Climate
Mel
tin
g s
easo
nG
row
ing
season
Local sea ice area anomalies associated with SST anomalies
Local sea ice area anomalies with sea ice thickness anomalies
SST persistence
Local SST anomalies impact sea ice area
anomalies
Local sea ice thickness anomalies impact sea
ice area anomalies
SIT persistence
Climate Forecasting Unit
II – Sea Ice Initialization
Guemas et al (2014) Climate Dynamics
NEMO3.2 ocean model + LIM2 sea ice model
Forcings : 1958-2006 DFS4.3 or 1979-2013 ERA-interim
Nudging : T and S toward ORAS4, timescales = 360 days below 800m, and 10 days above except in the mixed layer, except at the equator (1°S-1°N), SST & SSS restoring (-40W/m2, -150 mm/day/psu)
Wind perturbations + 5-member ORAS4 - - - > 5 members for sea ice reconstruction
5 member sea ice reconstruction for 1958-present consistent with ocean and atmosphere states used for initialization
Climate Forecasting Unit
Reconstruction IceSat
Too much ice in central Arctic, too few in the Chukchi and East Siberian Seas
2003-2007 October-November Arctic sea ice thickness
II – Sea Ice Initialization
Guemas et al (2014) Climate Dynamics
Climate Forecasting Unit
March and September Arctic sea ice
Sea ice area Sea ice volume
DFS4.3 + Nudging
ERAint + Nudging
UCL
HadISST NSIDC
DFS4.3 Free
ERAint + Nudging
DFS4.3 Free
UCL
PIOMAS
DFS4.3 + Nudging
Bias but reasonable agreement in terms of interannual variability
Th
ou
san
ds
km3
Mil
lio
ns
km2
II – Sea Ice Initialization
Guemas et al (2014) Climate Dynamics
Climate Forecasting Unit
II – Sea Ice InitializationAnomaly versus Full Field Initialization
EC-Earth2.3, 5 members, start dates every 2 years from 1960 to 2004
NOINI : historical simulation
FFI : Full-field initialization from ORAS4 + ERA
OSI-AI : Ocean and sea ice anomaly initialization with corrections to ensure consistency
rho-OSI-wAI : Ocean and sea ice weighted anomaly initialization to account for the different model and observed amplitudes of variability + (density, temperature) Instead of (temperature, salinity) anomaly initialisation
danila.volpi@ic3.cat
Climate Forecasting Unit
RMSE sea ice area. Ref: Guemas et al (2014)
RMSE sea ice volume. Ref: Guemas et al (2014)
NOINI NOINIFFI
FFI
OSI-AIOS
I-AI
rho-OSI-wAI rho-OSI-wAI
II – Sea Ice InitializationAnomaly versus Full Field Initialization
danila.volpi@ic3.cat
Lower forecast error when using ocean and sea ice anomaly initialization, even lower with weighted anomalies
Climate Forecasting Unit
Chevallier and Guemas (2014) in preparation
III – Multi-model Sea Ice Prediction
CNRM-CM5.1 and EC-Earth2.3
Seasonal forecasts initialized every 1st November and every 1st May from 1990 to 2008
5 month long
Initialized from ERA-interim for the atmosphere + in-home sea ice reconstructions + ORAS4 (Ec-Earth2.3) or ocean reconstruction (CNRM-CM5.1) for the ocean
5 members using initial perturbations applied to all components for EC-Earth2.3, only the atmosphere for CNRM-CM5
Climate Forecasting Unit
Chevallier and Guemas (2014) in preparation
III – Multi-model Sea Ice Prediction
Summer prediction
Winter prediction
Bering
Okh
otsk
Greenland
Barents
Kara
Baffin
Hudson
Climate Forecasting Unit
Chevallier and Guemas (2014) in preparation
III – Multi-model Sea Ice Prediction
Total Arctic Baffin Bay
Linearly Detrended Anomaly Correlation for Sea Ice Extent (SIE)
EC-Earth 2.3CNRM-CM5.1EC-Earth 2.3 + CNRM-CM 5.1
Predictability until March Similar performance between CNRM-CM5.1
and EC-Earth 2.3
95% confidence interval
correlation
Climate Forecasting Unit
Chevallier and Guemas (2014) in preparation
III – Multi-model Sea Ice Prediction
Greenland Sea Barents and Kara Seas
Linearly Detrended Anomaly Correlation for Sea Ice Extent (SIE)
EC-Earth 2.3CNRM-CM5.1EC-Earth 2.3 + CNRM-CM 5.1
Predictability for the first month only in Greenland, until March in Barents and Kara Better performance from CNRM-
CM5.1
95% confidence interval
correlation
Climate Forecasting Unit
Chevallier and Guemas (2014) in preparation
III – Multi-model Sea Ice Prediction
Okhotsk Sea Bering Sea
Linearly Detrended Anomaly Correlation for Sea Ice Extent (SIE)
EC-Earth 2.3CNRM-CM5.1EC-Earth 2.3 + CNRM-CM 5.1
Better initialisation in Okhotsk Sea with CNRM-CM5: ocean ? Multi-model allows to make the most of individual performance
95% confidence interval
correlation
Climate Forecasting Unit
Conclusions Sources of sea ice predictability: persistence, ice
thickness preconditioning, advection, ocean heat transport, reemergence
Initialization: 1. Need to make the most of the growing sea ice observations (thickness, melt pond, ice drift) 2. Need for ensembles consistent with the atmospheric and oceanic state
3. Need for further investigation of anomaly initialisation benefits
Prediction: winter predictability until March in the Baffin Bay, Kara, Barents and Okhotsk seas