Review of Delhasse, Kittel, and Beckmann: "Exploring the Greenland Ice Sheet’s response to future warming-threshold scenarios over 200 years"

Dear Authors and dear Editor:

For transparency: I reviewed an earlier version of this manuscript submitted to a different journal. Since then, the  manuscript has improved considerably and the current version addresses many of my previous comments.

Before I can recommend publication, I would like to ask the authors to address my comments below, most of which revolve around the writing quality and clarity.

Best,

Andy Aschwanden

University of Alaska Fairbanks

General Comments:

I recommend using acronyms sparingly as they make a manuscript less readable. In almost all cases, I find spelling it out improves the flow. Acronyms do have their place like for models like MAR or PISM or commonly used acronyms where the acronyms is better known that what it stands for (GPS, NASA, etc).

L 3: We explore responses to global atmospheric temperature increases from +0.6C to +5.8C since pre-industrial and...

L 5: "Our study then only..." First, I'm not sure what the "only" refers to (what are you not evaluating?) and second, "then" is commonly used in constructs like "First, we did this, second, we did that, then we..." Please clarify.

L 15: ...such as the Greenland Ice Sheet, are having...

L 18: "fourfold increase in ice loss" can you clarify whether or not this refers to rates of ice sheet mass change? Is it taken from table 2 in Otosaka 2023?

L 19: "Mass loss projection for the end of the 21st century..."

L 24: "causing the ice sheet to retreat". Please clarify. The ice sheet is already retreating, I assuming you mean that the Greenland Ice Sheet could disappear?

L 35-45 Paragraph requires some clarifications and disentanglement. Here is a suggestion based on what I think you are trying to say, modify and elaborate accordingly:

"All the previous studies overlook key processes..." I would change this to something like "Previous studies have a variety of shortcomings. Some studies employ standalone ice sheet models, ignoring, i.e., temperature and precipitation feedbacks between the ice sheet and the ice atmosphere (cite studies). Other studies use Earth System Models with interactive ice sheets (citations, e.g. Vizcaino 2015); while these models capture crucial feedbacks, their resolution of the atmosphere is often to coarse to resolve katabatic winds that impact surface melt, or their surface models can be biased because ...(elaborate). Polar-oriented regional climate models, by contrast, employ much higher resolutions than..., allowing for... However they lack the capability to simulate ice sheets, a limitation... 

L 47: We also investigate the ice sheet's response to an idealized reversion to the current...

L 54: ...coupled with the Parallel Ice Sheet Model (PISM, ...)

L 55: "Using MAR instead of a simpler energy balance model..." Rephrase, maybe something like

"Using MAR to downscale coarse atmospheric forcing, combined with MAR's sophisticated surface energy balance model comes at a high(er?) computation cost, but results in a more realistic reproduction of surface mass balance (cite a study showing that).

L 59: PSIM -> PISM

L 61: "the ice sheet model has a monthly time step". PISM uses an adaptive time step by default. Did you enforce a 1 month time step?

L 93-100. This is quite interesting and possibly worth a figure to visualize the non-linearity. How about plotting the sea level contribution (y axis) as a function of the per-degree increase in temperature (x axis)?

L 109-10: "the mass balance increasingly depends on surface mass balance, with a progressively smaller contribution from ice discharge through the grounding line."

L 128: clarify "over the same horizon"

L 132: "continuous" Do yo mean "irreversible"

L 134: What do you mean with "long term dynamics"?

L 142: "...remain relatively weak for global temperature increases below 1.4degC."

L 165: "In our experiment" -> "In our experiments"

L 179: "Ice discharge stabilizes around 2120 at about -230Gt/yr, causing the lag between SMB and mass balance turning positive.

L 199: "Even if the reverse experiment has a larger mass loss in 2200 than the +2.3 and +3.4degC experiments, its SMB in 2200 is higher, suggesting a lower SLC on time scales longer than considered here."

L 209: "The Greenland Ice Sheet's mass balance almost turns positive in 2200, despite the SMB being lower (231Gt/yr) compared to 2000--2010 (453Gt/yr)".

L 210-15: Can you elaborate on this: "leading to rapid ice loss at the end of the experiment, when the SMB and mass balance rapidly decline again". I don't see this rapid decline in Figure 2 or S1. It appears to decline a bit, but to me this looks more like inter-annual variability. "Ice discharge has decreased by 417Gt/yr favored by the GrIS thinning, compensating the lower surface accumulation ". Do you mean "lower surface mass balance" instead of "surface accumulation"? Also "favored by ... thinning" sounds odd to me. Can you rephrase? "This suggests...could be more stable..." I'm afraid I'm not following here. The Greenland Ice Sheet is currently not in an equilibrium state. Could you clarify what you mean?

L 266: "With a cautious..." I don't understand this sentence. Could you please rephrase it?

L 285: fix citation types from \citep to \cite.