CONCEPTS high resolution ice- ocean Arctic-Atlantic model: improving the ice Dept of National Defence F. Dupont, F. Roy, J.-F. Lemieux, G. Smith, Y. Lu, S. Higginson, R. Bourdalle-Badie and other CONCEPTS collaborators

Domain presentation: 1580x1817x procs (271 land procs removed) Extracted from ORCA12 (Mercator) with the north fold stitched back. Regional CONCEPTS domain (CREG). Resolution is maximum near the artificial pole over northern Canada at 1.8 km and minimum along the Atlantic northern boundary (8.2km) Covers part of North Atlantic (27N), the whole Arctic Ocean. Atmospheric forcing from 33km CGRF + GEWECS correction on SW/LW radiation (Smith et al. 2013, QJRMS) Typical location of the north fold on the ORCA family grid

First Rossby radius of deformation from Mercator ORCA12 ( ) Red: good resolution for eddies Blue: eddies under-resolved

~4 X 8-year hindcasts Hindcast 01: No-slip IC+OBC:GLORY S2 Vertical turbulence: 1.5 Gaspar LIM2-VP (20 pseudo- iterations) Hindcast 02: Free-slip IC+OBC: ORCA12 (free-run by Mercator) Vertical turbulence: 1.5 Gaspar LIM2-VP (20 pseudo- iterations) Hindcast 03-05: Free-slip IC+OBC: ORCA12 (free-run by Mercator) Vertical turbulence: k- epsilon CICE (EVP with 900 sub-iterations) H04 corrects a bug in salt flux and uses an increased Cw. H05 uses a reduced Zo for atm-ice.

Ice Area comparison: obs (black) against CREG12 (02=red, 04=purple) and ORCA12 (blue) Note that CREG2-04 (CICE-NEMO) shows a larger seasonal cycle (thin ice categories melt and growth faster) and a better fit to the September minimum

Ice Area comparison: obs (black) against CREG12 (02=red, 04=light red, 05=purple) and ORCA12 (blue) H04-H05 very close

2007 Summer minimum hindcast_01hindcast_02hindcast_04 ORCA12-Mercatorhindcast_05

ICESATCREG12-H02 Model -obs

CREG12-H05

Ice Volume comparison: CREG12 (02=red; 04=purple) and ORCA12 (blue)

Ice Volume comparison: PIOMAS=black, CREG12 (H02=red; H04=ligh red, H05=purple) and ORCA12 (blue)

Very large ice-velocity in CREG12 (small improvements in H04-H05 by increasing ice-ocean drag and decreasing ice-ocean drag) cm/s Obs Hindcast 01Hindcast 02 Obs cm/s Hindcast 05ORCA12

Ice velocity comparison: CERSAT against IABP (black), CREG12 (tones of red) and ORCA12 (blue circles)

Do high ice velocity translate into a high Beaufort gyre? Mean SSH H01 H02 H04H05

Fresh Water Content in the Beaufort Gyre from hindcast and ORCA12 compared to WHOI observations

Conclusions CICE implementation was a good improvement over LIM2, in terms of thermodynamics. Too thick ice in BG, too fast, even with reduced Zo. nonlinear feedback between Zo and upper winds in atmospheric model, turning angle, rheology still too weak? Too much transport in general through CAA, in Nares Strait in particular. Bathymetric sill missing? Hindcast with active tides under way. Coupling to our weather/climate model.

Embedded ice, focusing on the dynamic component Following Hibler et al. (2006, Ann. of.Glac.) Mass embedding is a question of volume and salt fluxes in a varying ocean vertical coordinate (in nemo convention z*) Dynamic embedding requires an implicit solution of the ice-ocean dynamics: our solution, IMplicit-EXplicit family-type, is to iterate between the ice-solver and the vertical implicit solver of the oceanic vertical momentum diffusion problem Can we converge? Ans=yes, if the problem is not too linear...

Why doing it? In our case, the ice-ocean drag coefficient was getting large enough (due to the thin surface layer and the logarithmic profile) that some numerical instabilities were resulting. 2 solutions: reduce the time-step move to an implicit solution in the ocean of the ice-ocean drag (previously explicit). But then, the resulting momentum is inconsistent with what the ice saw → need to iterate... Ice model Surface elevation solver Using an estimated Ice-ocean flux Vertical momentum solver (triagonal implicit) Ice dynamics Vertical momentum solver (triagonal implicit) conv?

Experiment with P*=25kNm, at 12km resolution over the Arctic, NEMO-LIM2-VP The creep parameter defines the minimum value of the deformation used in computing the viscosities (the smaller the creep, the larger the viscosities, the more nonlinear the solution becomes)

Canadian Global Forcing: Canadian Global Reforecasts (CGRFs) Smith et al. (submitted to QJRMS) CGRFs (33 km): –Recent version of our operational Global Deterministic Prediction System (GDPS) –Rerun from to –30hr forecasts for every day at 00Z (not a reanalysis, but does it matter?) –Continuous forcing set built with hour 7-30 (forecast spin up excluded) –Improvement with time due to evolving quality of analyses) –Using new 0.2° CMC global SST reanalysis (Brasnett 2008) –Important biases in SW, LW (bias corrections based on GEWEX available) –Better resolution than available reanalyses, e.g. –ERA-I (79 km) –NCEP-CFSR (38km) (but provided on 0.5deg)

Section across the Arctic from CAA to Russia CanadaRussia

Section across the Arctic from CAA to Russia CanadaRussia

Hindcast 02 Model currents unable to cross over Mendeleev Rise

Hindcast 05 Relatively similar to H04, but Beaufort Gyre seems to not extend as deep, since the cyclonic circulation at the rim of BG is slightly better

Ice forecast comparison for systems are compared: ORCA025 (global 1/4 th ), i.e. PSY3V3 Mercator system but with our own forcing and ice insertion (global analysis at 1/3 rd ), NEMO-LIM2EVP RIPS (regional domain centered over North America) based on CICE4 (EVP)+slab ocean at 5km. 3DVar analysis at 5km inserted. CREG12-LIM2VP (~H02): initialized from ORCA025 analysis; ice merged from RIPS and global analysis; shows a significant improvement over ORCA025 in RMS

RMS, bias and nb of points for ice fraction verification against CMC RIPS analysis: RIPS forecast (black), ORCA025 Fcst (blue) and CREG12 Fcst (red) Not quite comparing apple to apple (missing Bering Sea in CREG12) but promising CREG12-LIM2 in forecast mode