<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi Stanislav, what boundary conditions are you using? Where do they come from, what is the space and time resolution at which you apply them? One issue with sea ice boundary conditions is that even if you apply boundary conditions from an identical but larger-domain simulation, you can still get artifacts at the boundaries, convergence or divergence, if you are not applying full temporal frequency or if there are nonlinearities that cause the regional simulation to diverge relative to the larger-domain simulation.<div class=""><br class=""></div><div class="">Clement Bertin and other colleagues, cc-ed, are exploring options for sea ice boundary conditions for a McKenzie River Delta set-up and facing some of the same issues that you are. Ultimately, we are wondering if some region of relaxation around the edges might be the best practical solution to this problem.</div><div class=""><br class=""></div><div class="">Dimitris<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On May 18, 2020, at 11:19 AM, Yilang Xu <<a href="mailto:yxu@whoi.edu" class="">yxu@whoi.edu</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Hi Stanislav,<span class="Apple-converted-space"> </span><o:p class=""></o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">In my simulations, the major change is OBCS_SEAICE_AVOID_CONVERGENCE. This option will help to advect sea ice across the boundaries more freely, and reduce the noisy convergence that affects both the boundary and interior values. However, as the code says, the boundary sea ice conditions will be less accurate. I cannot remember my OBCS_SEAICE_COMPUTE_UVICE results, but it is definitely worth a try.<span class="Apple-converted-space"> </span><o:p class=""></o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Changing SEAICE_no_slip did not affect my results. But my setup is different from yours. You might want to do another test later to confirm it.<span class="Apple-converted-space"> </span><o:p class=""></o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Best,<span class="Apple-converted-space"> </span><o:p class=""></o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Yilang<span class="Apple-converted-space"> </span><o:p class=""></o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="border-style: solid none none; border-top-width: 1pt; border-top-color: rgb(181, 196, 223); padding: 3pt 0in 0in;" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span style="font-size: 12pt;" class="">From:<span class="Apple-converted-space"> </span></span></b><span style="font-size: 12pt;" class="">MITgcm-support <<a href="mailto:mitgcm-support-bounces@mitgcm.org" style="color: blue; text-decoration: underline;" class="">mitgcm-support-bounces@mitgcm.org</a>> on behalf of Stanislav Martyanov <<a href="mailto:martyanov.sd@gmail.com" style="color: blue; text-decoration: underline;" class="">martyanov.sd@gmail.com</a>><br class=""><b class="">Reply-To:<span class="Apple-converted-space"> </span></b><<a href="mailto:mitgcm-support@mitgcm.org" style="color: blue; text-decoration: underline;" class="">mitgcm-support@mitgcm.org</a>><br class=""><b class="">Date:<span class="Apple-converted-space"> </span></b>Monday, May 18, 2020 at 13:38<br class=""><b class="">To:<span class="Apple-converted-space"> </span></b><<a href="mailto:mitgcm-support@mitgcm.org" style="color: blue; text-decoration: underline;" class="">mitgcm-support@mitgcm.org</a>><br class=""><b class="">Subject:<span class="Apple-converted-space"> </span></b>Re: [MITgcm-support] SEAICE, very thick ice<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Hello, Ma<span style="" class="">rtin and Yilang!</span><o:p class=""></o:p></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="background-color: white;" class="">I thank you for your adv</span><span style="font-family: Arial, sans-serif; background-color: white;" class="">ices and I will report of the results after I try these options.</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: Arial, sans-serif; background-color: white;" class="">I will start from setting SEAICEpressReplFac=1 and see if it helps. After I will try OBCS_SEAICE_AVOID_CONVERGENCE and OBCS_SEAICE_COMPUTE_UVICE, together or one after another.</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: Arial, sans-serif; background-color: white;" class="">Previously I was thinking about </span>OBCS_SEAICE_AVOID_CONVERGENCE <span style="font-family: Arial, sans-serif; background-color: white;" class="">but did not want to use any 'old' implementations, whatever it means.. Also I was looking at the options </span><span style="background-color: white;" class="">SEAICE_no_slip option and </span><span style="font-size: 12pt; font-family: "Times New Roman", serif; background-color: white;" class="">SEAICEsimpleRidging..</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" width="0" style="width: 0in; border-collapse: collapse;"><tbody class=""><tr style="display: flex;" class=""><td width="1242" nowrap="" valign="top" style="width: 931.75pt; padding: 0in; max-height: 20px;" class=""><table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" width="1242" style="width: 931.5pt; border-collapse: collapse;"><tbody class=""><tr class=""><td style="padding: 0in; display: flex;" class=""><h3 style="margin: inherit; font-size: 13.5pt; font-family: Calibri, sans-serif; line-height: 15pt; text-overflow: ellipsis; overflow: hidden;" class=""><span class="gmail-gd"><span style="font-size: 10pt; font-family: Arial, sans-serif; letter-spacing: 0.15pt; background-color: white;" class="">Yilang</span></span><span style="letter-spacing: 0.25pt;" class=""><o:p class=""></o:p></span></h3><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span style="font-family: Arial, sans-serif; letter-spacing: 0.15pt; background-color: white;" class=""><br class=""><br class=""></span></b><o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: Arial, sans-serif; letter-spacing: 0.15pt; background-color: white;" class=""><br class=""><br class=""></span><o:p class=""></o:p></div></div></td></tr></tbody></table></td></tr></tbody></table><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: Arial, sans-serif; background-color: white;" class="">Did you use anything besides OBCS_SEAICE_AVOID_CONVERGENCE to handle such situation in your simulations? Did you play with SEAICE_no_slip option? If yes - does it really affect the results?</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span style="font-family: Arial, sans-serif; background-color: white;" class="">Martin</span></b><o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">>> This is only implemented for OBCS_UVICE_OLD <o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Can't I just use OBCS_UVICE_OLD in the current version (c67p)?<o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: Arial, sans-serif;" class="">In our previous simulations (another model configuration) we did not set uice and vice at the OBs at all, and we also did not use </span>OBCS_SEAICE_COMPUTE_UVICE (checkpoint c65z).<span style="font-family: Arial, sans-serif;" class=""> </span>May be<span style="font-family: Arial, sans-serif;" class=""> </span>such approach<span style="font-family: Arial, sans-serif;" class=""><span class="Apple-converted-space"> </span>can help in the current situation, or it does not really matter?</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-family: Arial, sans-serif;" class="">Stanislav</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div class=""><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">пн, 18 мая 2020 г. в 19:41, Martin Losch <<a href="mailto:Martin.Losch@awi.de" style="color: blue; text-decoration: underline;" class="">Martin.Losch@awi.de</a>>:<o:p class=""></o:p></div></div><blockquote style="border-style: none none none solid; border-left-width: 1pt; border-left-color: rgb(204, 204, 204); padding: 0in 0in 0in 6pt; margin-left: 4.8pt; margin-right: 0in;" class="" type="cite"><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Hi Stanislav,<br class=""><br class="">the open boundary conditions for sea ice were probably not made for this type of situation (have them in the middle of an active ice region where ice is confined by topography).<span class="Apple-converted-space"> </span><br class=""><br class="">One thing that will always reduce excessive ridging is turning off the default pressure replacement method (set SEAICE_pressReplFac = 0.). With pressure replacement, stagnant ice tends to be pushed and piled up in corners and bays, because the replacement pressure (so the ice strength) reduces dramaticall for small strain rates (when nothing is moving anymore).<br class=""><br class="">other than that, I would probably try the option “OBCS_SEAICE_COMPUTE_UVICE”. This is only implemented for OBCS_UVICE_OLD, but you can easily transfer that implementation of a Neumann boundary conditions (du/dn = 0 across the boundary) from seaice_adjust_uvice.F to seaice_apply_uvice.F In this way, the ice velocities will be determined only by forcing in the interior.<span class="Apple-converted-space"> </span><br class=""><br class="">But you should maybe first check, if you have excessive flux of ice over your boundaries. At least the northwest corner doesn’t look like that in your plots.<br class=""><br class="">Martin<br class=""><br class="">> On 18. May 2020, at 17:38, Stanislav Martyanov <<a href="mailto:martyanov.sd@gmail.com" target="_blank" style="color: blue; text-decoration: underline;" class="">martyanov.sd@gmail.com</a>> wrote:<br class="">><span class="Apple-converted-space"> </span><br class="">> Hello everyone!<br class="">> <span class="Apple-converted-space"> </span><br class="">> I get very thick sea ice at several locations in the high-res Kara Sea model domain (horizontal resolution is 500-1200 m). Interestingly, the general pattern of sea ice concentration and thickness is OK compared to MERCATOR ocean reanalysis, but in some regions the modeled HEFF is reported by the monitor to be about 15 m after 5 months of integration (starting from realistic initial conditions). I have attached the figure to clarify what I mean and where it happens.<br class="">> <span class="Apple-converted-space"> </span><br class="">> I suspect the ridging process near the open boundaries to be involved in this situation, but I do not know what can be done with it.<br class="">> <span class="Apple-converted-space"> </span><br class="">> Such HEFF also produce problems in vertical layers when useRealFreshWaterFlux is TRUE, but I checked that such too thick ice is also produced when useRealFreshWaterFlux is OFF, so it is not a cause (at least, not the main cause).<br class="">> <span class="Apple-converted-space"> </span><br class="">> Unfortunately, there exist too many options to just iterate through all of them.<br class="">> <span class="Apple-converted-space"> </span><br class="">> May be you can advise what can be done to mitigate such overestimated HEFF? My preliminary suggestions are as follows, but I am not sure about them:<br class="">> <span class="Apple-converted-space"> </span><br class="">> - to switch off the uice and vice at the OBCS?<br class="">> - to set SEAICE_no_slip=TRUE to reduce the sea ice velocities near the coasts to prevent enhanced ridging?<br class="">> - to use sponge at the open boundaries?<br class="">> - there was a CPP key OBCS_SEAICE_AVOID_CONVERGENCE, but it is only for OBCS_UVICE_OLD which, in turn, is undefined by default and even may be not implemented, as stated.<br class="">> <span class="Apple-converted-space"> </span><br class="">> Any advice is very welcome!<br class="">> <span class="Apple-converted-space"> </span><br class="">> Stanislav<br class="">> <br class="">> PS: I use a SEAICE package configuration which is very close to the default one. What I have changed is:<br class="">> #define SEAICE_VARIABLE_SALINITY<br class="">> SEAICEadvScheme = 33,<br class="">> SEAICE_multDim = 1,<br class="">> <SEAICE_OPTIONS.h><data><CPP_OPTIONS.h><OBCS_OPTIONS.h><data.obcs><FIGURE HEFF.png>_______________________________________________<br class="">> MITgcm-support mailing list<br class="">><span class="Apple-converted-space"> </span><a href="mailto:MITgcm-support@mitgcm.org" target="_blank" style="color: blue; text-decoration: underline;" class="">MITgcm-support@mitgcm.org</a><br class="">><span class="Apple-converted-space"> </span><a href="http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support" target="_blank" style="color: blue; text-decoration: underline;" class="">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support</a><br class=""><br class="">_______________________________________________<br class="">MITgcm-support mailing list<br class=""><a href="mailto:MITgcm-support@mitgcm.org" target="_blank" style="color: blue; text-decoration: underline;" class="">MITgcm-support@mitgcm.org</a><br class=""><a href="http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support" target="_blank" style="color: blue; text-decoration: underline;" class="">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support</a><o:p class=""></o:p></div></blockquote></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">_______________________________________________ MITgcm-support mailing list<span class="Apple-converted-space"> </span><a href="mailto:MITgcm-support@mitgcm.org" style="color: blue; text-decoration: underline;" class="">MITgcm-support@mitgcm.org</a><a href="http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support" style="color: blue; text-decoration: underline;" class="">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support</a><o:p class=""></o:p></div></div><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">_______________________________________________</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">MITgcm-support mailing list</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><a href="mailto:MITgcm-support@mitgcm.org" style="color: blue; text-decoration: underline; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">MITgcm-support@mitgcm.org</a><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><a href="http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support" style="color: blue; text-decoration: underline; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support</a></div></blockquote></div><br class=""></div></body></html>