Loading...
Please wait, while we are loading the content...
Similar Documents
Response to reviewer comments
| Content Provider | Semantic Scholar |
|---|---|
| Author | Gladstone, Rupert R. M. |
| Abstract | in my view, the "transition zone" is best viewed not so much where ice lifts off the bed that would be the grounding line, which in a depth-integrated model is not a zone but generally a curve, and "resolving" that curve is probably not what is meant by "Adequate resolution." I am not sure what neutral equilibrium has to do with this; to my understanding there is no indication that marine ice sheets exhibit "neutral equilibrium" in the sense of Hindmarsh (implying a locally non-unique steady state grounding line position) We changed the text to “with the goal of reaching steady state.” page 367 line 6 "Another type of basal water channel forms through pressureinduced melt. Channels of this type that form within 50 to 100km of the grounding line are also likely to connect to the ocean (Cuffey and Paterson, 2010)." I’m not sure what you are talking about here (a page reference to Cuffey and Paterson may help). Pressureinduced melt for a start is a thorny subject; all that pressure does is to change the melting point. The melting has to come out of assorted heat fluxes or heat sources — geothermal and frictional heating being the obvious candidates. In fact, I would avoid talking at all about hydrology to the extent that the paper currently does, as doing so suggests you will actually be modeling the processes that control effective pressure (which would be untrue). As far as I can see, the main argument here is that you expect effective pressure N to be continuous up to the grounding line, where it is zero. This will ensure that the basal shear stress goes continuously to zero as the grounding line is approached, which makes the numerically difficult discontinuity in b go away. Furthermore, this can be done in a τ way that the sliding law inland agrees with the sliding law used for instance in the MISMIP experiments. That argument could be stated in a single sentence (or maybe two) without getting tied up in extraneous physical processes and observations that actually raise more questions about the model in this paper (for instance, lake drainage is clearly non-steady and there is not necessarily a persistent hydrological syste; if there is channelized drainage, its effects on effective pressure at the bed could be quite localized). If you do wish to persist with the present list of reasons, beware any spurious arguments about tides making your formulation more appropriate — if you want tides, you might have to start resolving the migration of the grounding line over the tidal cycle and its time-integrated effect on the evolution of mean grounding line position, which presumably starts to involve a rather complicated viscoelastic formulation. I’d want to stay well away from that. We agree that this discussion of detailed hydrology processes could mislead the reader. We substantially cut this paragraph, including the references to pressure-based melting and tides. The remaining text is intended to suggest the possibility of connections between subglacial drainage systems and the grounding line, so as to motivate our effective-pressure parameterization without suggesting it represents other detailed processes. page 367 line 28: "Based on this parameterization we give a new definition of the transition zone." see comments at the start of the review regarding the meaning of a "transition zone" We removed this sentence. In Section 2.2 (third from last paragraph) we now define what we call the “friction transition zone,” which is distinct from (but related to) “the transition zone” as defined above. page 368: I’m not a fan of the l + b + d notation. Even though l has units of τ τ τ τ stress, it is actually the divergence of a depth-integrated stress. Equation (2) also obscures the fact that we are looking at a second-order elliptic problem for u. Also, the sign convention for b is odd, as it requires the sliding law to be stated τ with a minus sign throughout the rest of the paper. I’d suggest switching b to b τ τ everywhere to agree with standard glaciological usage. We agree that although b and d are stresses, l is actually the divergence τ τ τ of a depth-integrated stress. We changed the notation accordingly. We replaced l with (Hτl)x, where in the new expression, l is the vertically τ τ averaged longitudinal stress. We also switched the sign of b as τ |
| File Format | PDF HTM / HTML |
| DOI | 10.5198/jtlu.2017.1006.s384 |
| Alternate Webpage(s) | https://www.the-cryosphere-discuss.net/8/C629/2014/tcd-8-C629-2014-supplement.pdf |
| Alternate Webpage(s) | https://www.solid-earth-discuss.net/se-2019-9/se-2019-9-AR1.pdf |
| Alternate Webpage(s) | https://doi.org/10.5198/jtlu.2017.1006.s384 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Letter |
