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Hi MITgcm community, </div>
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<span style="background-color:rgb(255, 255, 255);display:inline !important">I'm using MITgcm with set-up similar to Horvat et al. 2016 (75 by 75 km at 2 km resolution, zonally re-entrant channel, northern half sea ice covered, hydrostatic). The ocean is cooling
everywhere, sea ice forming with thsice package. </span>I am having some issues with grid scale noise and large values of the vertical velocity field. I have tried a few adjustments so far: I turned<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;"> KPP
smoothing options on, to no effect, and next I tried using different viscosities/tuning the viscosity constants using examples in the MLAdjust tutorial. Using modified Leith & Smagorinsky, noise reduction only happens in the model when I increase the viscosity
constants by up to 2 orders of magnitude, but increasing them this much also dampens the dynamics, reducing magnitude of the zonal jet. </span></div>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">For reference, I've attached an image with snapshots </span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;"></span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">of
</span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">zonal & vertical velocity fields, model day 105, for</span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;"> a
range of viscosity constant values from 1.85 -> 250, all using modified Leith & Smagorinsky. T<span style="background-color:rgb(255, 255, 255);display:inline !important">he subplot titles e.g 'UVEL LS30' stand for velocity field + viscosities used (all Leith
and Smag. here, or LS) + the value used for every viscosity constant. </span></span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">I've also attached an example data file to this email. Increasing the
viscosity constants reduces the vertical velocity from ~ 4e-4 m/s to 1e-4 m/s, but also the zonal jet by ~ factor 2. </span></div>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">I have also tried also using Leith & Smagorinsky individually, QGLeith, harmonic/biharmonic but all to little avail unfortunately. </span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">Any
help would be much appreciated, </span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">if anyone has an idea of what could be the issue, or further adjustments to try</span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">.</span></div>
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Many thanks, </div>
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Lily </div>
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