<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=Windows-1252">
</head>
<body>
<p>Hi Sara,</p>
<p><br>
</p>
<p>With the conventional approach, melting/freezing doesn't really
occur. In each horizontal grid cell, the ice thickness remains
constant. A melt rate is calculated, but only so that the correct
amount of heat and salt are added into the ocean beneath the ice.
"Melting", for example, removes heat from grid cell below the ice
shelf and effectively removes salt (essentially equivalent to
diluting with freshwater). <br>
</p>
<p><br>
</p>
<p>This addition/removal of heat/salt is what I think you're getting
at when mentioning the tendency. If you know the temperature and
salinity in the cell vertically adjacent to the ice, together with
its velocity (to parameterize turbulent transfers), then you have
everything you need to calculate the boundary. It can seem like a
chicken–egg problem, but there are standard ways to deal with the
heat flux into the ice to ensure the problem is solvable, e.g.,
the so-called three-equation formulation.<br>
</p>
<p><br>
</p>
<p>You mention you want a dynamic ice shell, so you might need to
use the remeshing add on for the SHELFICE package. I haven't
personally used it, but it is worth a look.</p>
<p><br>
</p>
<p>As for why we don't use a dense grid near the boundary, that's
because the MITgcm works on a fixed vertical grid. Unless the ice
shelf draft is everywhere the same, you can't always have a highly
resolved grid below the ice.</p>
<p><br>
</p>
<p>If you haven't done so already, work through the Losch (2008)
paper, which describes the physics behind the package.<br>
</p>
<p><br>
</p>
<p> Ken</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 2021-06-02 1:20 p.m., Miller, Sara G
wrote:<br>
</div>
<blockquote type="cite" cite="mid:MN2PR07MB69445368B2627F9FBFDE87EAD13D9@MN2PR07MB6944.namprd07.prod.outlook.com">
<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>
<p><span style="color:#D73F09;">[This email originated from
outside of OSU. Use caution with links and attachments.]</span></p>
<div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
Hello all,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
I am trying to understand the treatment of the ice-ocean
boundary layer in the SHELFICE package. My goal is to use
MITgcm to model a dynamic, global ice shell over an ocean on
Jupiter's moon Europa. I believe the SHELFICE package will be
useful for me, but I do not fully understand the description
given in the user manual regarding boundary layer modeling. </div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;"><br>
</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;">What is the total
tendency and how is it used in the calculation of the
boundary layer temperature at a future time step? The
boundary layer temperature and freezing/melting information
feels like a chicken-and-egg problem. It would make sense to
me that you need to know the temperature in the BL to
determine if you're in the freezing or melting regime, but
MITgcm shows boundary layer temperature as a function of
that total tendency term which I think captures the
freezing/melting information. </span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;"><br>
</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;">More fundamentally,
how do you melt the ice in MITgcm? Does it slowly melt until
it passes the threshold to step up to the next grid, or does
its pressure just change? That is, the ice base is always
the first grid cell, and as it melts upwards the pressure
term just changes with it. I am new to modeling, but </span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;">I don’t understand
why we’re working in fractions of a grid cell instead of
just making the grid more densely-spaced in the boundary
layer region.</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;"><br>
</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;">I apologize for the
volume of questions in a single email! I appreciate any and
all wisdom/advice.</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;"><br>
</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;">Best regards,</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial,
Helvetica, sans-serif; font-size: 12pt;">Sara</span></div>
<div>
<div style="font-family: Calibri, Arial, Helvetica,
sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica,
sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
---</div>
<div id="Signature">
<div>
<div id="divtagdefaultwrapper" dir="ltr" style="font-size:12pt; color:#000000;
background-color:#FFFFFF;
font-family:Calibri,Arial,Helvetica,sans-serif">
Sara G. Miller (she/her)
<div>PhD Student </div>
<div><span style="font-family:Calibri,Arial,Helvetica,sans-serif;
background-color:rgb(255,255,255);
display:inline!important">Georgia Institute of
Technology</span><br>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
MITgcm-support mailing list
<a class="moz-txt-link-abbreviated" href="mailto:MITgcm-support@mitgcm.org">MITgcm-support@mitgcm.org</a>
<a class="moz-txt-link-freetext" href="http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support</a>
</pre>
</blockquote>
</body>
</html>