NACLIM annual meeting 2014, Berlin

Predictability of North Atlantic upper-ocean salinity(Work in progress)

Katja Lohmann, Daniela Matei, Johann Jungclaus, Manfred Bersch, Helene Langehaug and Yongqi Gao

Motivation

• Predictive skill of subpolar upper-ocean temperature for lead times of five to ten years due to northward advection of warm (and saline) subtropical water (Matei et al., 2012 *)

• Similar idea for sea surface temperature in eastern Nordic Seas (talk by Helene Langehaug)

* Matei, D., H. Pohlmann, J.H. Jungclaus, W.A. Müller, H. Haak and J. Marotzke (2012): Two tales of initializing decadal climate prediction experiments with the ECHAM5/MPI-OM model. Journal of Climate, 25, 8502–8523

Data

• Initialized hindcast prediction experiments from CMIP5 (so far MPI-ESM-LR); initialized every year 1960 to 2010

MPI-ESM-LR: Northern grid pole in Greenland; horizontal resolution in North Atlantic of 15 to 100 km Upper-ocean salt content (0 - 500m)

• CliSAP salinity dataset: combining salinity observations from different sources Atlantic 30ºN - 70ºN ; 1951 - 2005 (3 year running means)

MPI ocean model simulation forced with NCEP/NCAR reanalysis

Correlation hindcasts – CliSAP upper-ocean salt content

Correlation hindcasts – NCEP forced simulation

Correlation hindcasts – CliSAP upper-ocean salt content

RMSE hindcasts – CliSAP upper-ocean salt content

Time evolution of subpolar upper-ocean salt content

Conclusions (Work in progress)

Based on CMIP5 MPI-ESM-LR hindcasts:

• Largest predictability of North Atlantic upper-ocean salinity in western subpolar region; skillfull predictable < 5 years

• Predictability based on initialized hindcasts well above predictability from transient 20C simulations; but not above persistence forecast

• No predictive skill in eastern subpolar region due to hindcasts not capturing mid-1990s shift

• High predictability along STG/SPG boundary (German RACE project)

Correlation hindcasts – CliSAP SSS for EC Earth model

Outlook

• Extend analysis to CMIP5 models providing hindcasts initialized every year

• NorCPM hindcasts if available in time

• Compare with results from MPI PreCMIP5 hindcasts (German RACE project)

• Ishii salinity dataset (Japan Marine Science and Technology Center) to cover entire Nordic Seas

Thank you!

The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013) under grant agreement n.308299 (NACLIM).