Recent trends in energy flows through the Arctic climate system. Michael Mayer Leo Haimberger

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1 Recent trends in energy flows through the Arctic climate system Michael Mayer Leo Haimberger

2 Motivation and outline Arctic climate system is subject to rapid changes and large interannual variability How does this affect its energy budget? Investigate the observations-based coupled energy budget of atmosphere and ocean, including sea ice à Quantify accumulation of energy in the Arctic à Diagnose variability and trends in energy flows Decadal trends of reflected SW radiation (from Hartmann and Ceppi 2014)

3 Atmosphere Framework and data Rad TOA : satellite data (CERES)! " F A : mass-corrected from ERA-Interim, JRA55 F S : indirectly from atmospheric budgets Ocean! " F A = Rad TOA # F S # AET! " F O = (1-f i )F S +f i F IB -OHCT! " F O : direct estimates only from cross-sections: C-GLORSv5, ORAS4 (soon: in-situ transports from ARCGATE) OHC(T): C-GLORSv5, ORAS4, ORAP5, Hadley EN4 Sea ice! " F I = f i F S -f i F IB -IHCT Sea ice mass: C-GLORSv5, ORAP5, PIOMAS Note: IHCT here means energy going into ice melt

4 Accumulated arctic cap (70N-90N) energy anomalies OHC (C-GLORS) OHC (Hadley EN4) Ice melt (PIOMAS) Ice melt (C-GLORS) Long-term evolution Strong upward trend in OHC in-situ based OHC from Hadley EN4 very unstable due to lack of obs Comparatively little energy going into melt

5 Accumulated arctic cap (70N-90N) energy anomalies OHC (C-GLORS) OHC (Hadley EN4) Ice melt (PIOMAS) Ice melt (C-GLORS) OHC + ice melt (C-GLORS) Long-term evolution Strong upward trend in OHC in-situ based OHC from Hadley EN4 very unstable due to lack of obs Comparatively little energy going into melt

6 Long-term evolution How well do boundary fluxes replicate energy accumulation? OHC + ice melt (C-GLORS)

7 Long-term evolution How well do boundary fluxes replicate energy accumulation? OHC + ice melt (C-GLORS) F S + F (CERES/JRA55/C-GLORS) F S + F (CERES/ERA-I/C-GLORS) Periods of weak and enhanced ocean energy take-up agree quite well! Varying contributions from radiation and lateral transports

8 Storage anomalies vs flux anomalies Year-to-year (Oct-Oct) storage ( ) Good qualitative agreement between annual variation of accumulated energy changes in the arctic cap (r=0.83) Ocean energy variance lower than flux variance à regression coefficient only ~0.5 Jm - 2 /Jm /10 minus 2012/10 Accumulated flux anomalies [10 8 Jm - 2 ]

9 Variability: Budget time series for 70N-90N Clear relationship between surface energy flux and sea ice extent F S Sea ice fraction (NSIDC)

10 Variability: Budget time series for 70N-90N Clear relationship between surface energy flux and sea ice extent F S Sea ice fraction (NSIDC)

11 Variability: Budget time series for 70N-90N Clear relationship between surface energy flux and sea ice extent Atmospheric energy transport exhibits strong variability, especially associated with low ice extents in 2011, 2012 F Rad TOA F S Sea ice fraction (NSIDC)

12 Variability: Budget time series for 70N-90N Also clear relationship between surface flux and ocean energy terms! F Rad TOA F S OHCT (C-GLORS) IHCT (PIOMAS) IHCT (C-GLORS)

13 Seasonal trends: atmosphere Positive summer trend of FS driven by RadTOA à ice-albedo feedback Negative autumn trend of FS driven by atmospheric energy convergence associated with decreased baroclinicity!" # FA RadTOA Surface flux [K 1000km-1decade-1] (CERES) (CERES+reanalysis ensemble) (reanalysis ensemble) (ERA-I) T@925hpa

14 Seasonal trends: atmosphere Positive summer trend of FS driven by RadTOA à ice-albedo feedback Negative autumn trend of FS driven by atmospheric energy convergence associated with decreased baroclinicity!" # FA RadTOA Surface flux [K 1000km-1decade-1] (CERES) (CERES+reanalysis ensemble) (reanalysis ensemble) (ERA-I) T@925hpa

15 Seasonal trends: ocean and ice Changes in energy used for melting/freezing consistent with FS changes interesting temporal structure in ice melt trends Very noisy OHCT trend picture Surface flux OHC tendency Melting/freezing (CERES+reanalysis ensemble) (C-GLORS V5) (C-GLORS V5)

16 Seasonal trends: ocean and ice Changes in energy used for melting/freezing consistent with FS changes interesting temporal structure in ice melt trends Very noisy OHCT trend picture Surface flux OHC tendency Melting/freezing (CERES+reanalysis ensemble) (C-GLORS V5) (C-GLORS V5)

17 Seasonal trends 2000/ /02 Clear trend of atmospheric transports and surface fluxes in fall Significant amplification of oceanic annual cycle F (ERA-I + JRA55) Rad TOA (CERES) F S (from atmos budgets) OHCT + IHCT (C-GLORS) IHCT (C-GLORS) OHCT (C-GLORS)

18 Summary Recent changes in the Arctic have profound impact on its energy budget: Significant increase of Arctic energy content with varying contributions from lateral transports and radiation at TOA Yearly cycle of surface energy flux and heat storage in the Arctic is amplified à clear signal of ice-albedo feedback Reduced baroclinicity reduces atmospheric energy convergence during fall à where is it transported to instead? Technical issues remain, mainly concerning the mass budget Need for mass-consistent fields of ocean energy divergence Best practice how to deal with ocean mass variations required