the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 17 Oct 2025
Characterizing runoff response to rainfall in permafrost catchments and its implications for hydrological and biogeochemical fluxes in a warming climate
Abstract. Understanding how Arctic catchments respond to rainfall is critical for anticipating hydrological and biogeochemical effects of a warming climate. We use ensemble rainfall-runoff analysis (ERRA) to identify how runoff response to rainfall varies with meteorological, subsurface, and geomorphic conditions across three permafrost catchments: Upper Kuparuk (Alaska) and the Goose and Ptarmigan catchments (Cape Bounty, Canadian High Arctic). ERRA enables us to quantify event-scale runoff responses to rainfall using high-resolution, multi-year hydrometeorological datasets, and test how variations in rainfall intensity, thaw depth, antecedent wetness, and active layer detachments (ALDs) affect runoff behavior. Our results show that peak runoff response increases by more than five-fold in response to increases in antecedent streamflow (a proxy for antecedent moisture), and is also higher in summers with higher average precipitation. By contrast, warmer winters and springs, likely linked to deeper thaw and increased subsurface storage capacity, are associated with reduced runoff sensitivity to rainfall. Furthermore, a paired watershed comparison shows that streamflow and riverine fluxes of dissolved solids, suspended sediment, and particulate organic carbon are more readily mobilized by rainfall inputs when ALDs are present. Considered together, these findings highlight the difficulty in generalizing climate-driven runoff trends in permafrost regions subject to competing and interacting controls, such as precipitation intensity, storage capacity and permafrost stability. Our findings offer a more nuanced alternative to broad classifications of Arctic landscapes as “drying” or “wetting” under climate change.
- Preprint
(3869 KB) - Metadata XML
-
Supplement
(1748 KB) - BibTeX
- EndNote
Status: open (until 07 Dec 2025)
- RC1: 'Comment on egusphere-2025-4275', Anonymous Referee #1, 19 Nov 2025 reply
-
RC2: 'Comment on egusphere-2025-4275', Anonymous Referee #2, 20 Nov 2025
reply
This manuscript describes an application of the Ensemble Rainfall Runoff Analysis framework developed by Kirchner (2022), who is a co-author on this paper. The original theoretical framework was applied in a proof of concept by Kirchner (2024). This is the first application of the ERRA framework to an Arctic environment. The authors utilize long-term rainfall and discharge data from the Kuparuk River (Alaska, USA) and similar data augmented with material concentrations (e.g., DOC, SS) from two smaller catchments in Canada, to explore how well-known seasonal changes in active layer depth and surficial disturbance (active layer detachments) affect runoff and material transport in response to rain events. The authors then speculate on how expected changes in rainfall and surface air temperature may change runoff and material transport in the future. I think the greater value of this analysis is the information it provides about the credibility of the ERRA approach in a new environment. The analysis does less to increase our current understanding of the seasonal hydrology of Arctic headwater landscapes as they function now or as they may function in the future. This paper provides another useful proof of concept of the ERRA framework, which is likely to be of increasing utility as more and longer high-frequency solute datasets are developed to complement high-frequency rainfall and runoff data.
I have numerous suggestions for the authors to consider, that I think could improve this manuscript. In the following comments “L##s” refer to line numbers in the manuscript and are followed by the relevant text. The text following “Reviewer:” is my comment or suggestion.
L51: seemingly impermeable
Reviewer: Vague. Replace with "continuous"? Delete?L 74: Rainfall
Reviewer: Perhaps link the paragraph to the previous one with "On the other hand..."?L85-86: For example, McNamara et al. (1998) investigated rainfall–runoff response over three years at four distinct catchment scales but faced challenges in identifying the causes of annual changes.
Reviewer: Other more recent citations could be added. For example:- Shogren, A. J., et al. (2022), Multi-year, spatially extensive, watershed-scale synoptic stream chemistry and water quality conditions for six permafrost-underlain Arctic watersheds, Earth Syst Sci Data, 14(1), 95-116, doi:10.5194/essd-14-95-2022.
- Shogren, A. J., J. P. Zarnetske, B. W. Abbott, F. Iannucci, R. J. Frei, N. A. Griffin, and W. B. Bowden (2019), Revealing biogeochemical signatures of Arctic landscapes with river chemistry, Sci Rep-Uk, 9, doi:ARTN 12894. 10.1038/s41598-019-49296-6.
L152: or aufeis
Reviewer: To be accurate, perhaps say "or extensive aufeis" as there is some limited, seasonal aufeis in the mid-catchment.L 154-156: Roughly two-thirds of summer precipitation leaves the catchment as streamflow (McNamara et al., 1998), implying that evapotranspiration is a relatively small component of the water balance.
Reviewer: I don’t think you can infer that ET is small on this basis. Given this data only, ET is somewhere between “small” and 1/3 of summer precipitation. Either delete this final statement or clarify that unknown portions of the 1/3 balance went ET, temporary soil storage, and/or deeper percolation (which may occur even in “continuous” permafrost).L21-218: typical environmental time series are characterized by autocorrelated noise
Reviewer: It would be helpful to identify typical sources (types) of this autocorrelated noise. Some are described in Kirchner (2024).L222: where now beta-k
Reviewer: beta-k is not a part of equation 2. What is intended here?L222: Equation 15 of Kirchner, 2022
Reviewer: Equation 2 in this manuscript does not conform to Equation 15 in Kirchner 2022, which is a matrix. Do you mean Equation 11 in the latter?L226: b sub k
Reviewer: This parameter does not appear to be defined, nor is h as an index value.L269: Second instance of "predictor"
Reviewer: Should be "predictorS"? PluralL279-281: Given that the material flux data are only available for 92 individual days, we set the maximum response time to be 5 days (m = 5 days in Eq. (1) ) to avoid overfitting.
Reviewer: Are these single observations on 92 different days? If so, how do you account for the likelihood that identical points in different hydrographs may be associated with different levels of material concentrations? I understand how this works when the time series are continuous/regular and the time intervals are small, but not when the measurements are infrequent/random and the time intervals are large.L295-296: up to an apparent saturation point
Reviewer: It is interesting to note that this asymptote is at a discharge of about 0.11 mm/h which translates to 4.4 m3/s for the Kuparuk. This is well above the median flow and closer to bankfull.L300: 300 hours
Reviewer: This is nearly two weeks (12.5 days). How to subsequent storms and thaw runoff that is independent of rainfall influence this RRD curve?L320-323: This saturation threshold may represent the point at which water tracks become hydrologically connected to stream channels, enabling efficient runoff without requiring full saturation of the entire landscape, consistent with modeling results within the basin (Stieglitz et al., 2003).
Reviewer: What is meant by "efficient runoff" and "full saturation" of the watershed? It is not clear to me that "full saturation of the entire landscape" is a requirement to display the runoff behavior depicted in Figure 2c.L327: Figure 3.
Reviewer: It’s a minor point, but why connect the dots in panel 3c but not 3b?L351: Figure 4.
Reviewer: Why is the lag range in Fig 4a so much smaller than the lag range in either Fig. 3a or (especially) Fig. 2a? Shouldn't these be similar?L 354-355: aggregating hourly Upper Kuparuk time series to 4-hour intervals
Reviewer: Why change the intervals from 10 h bins to 4 h bins?L365-366 (and Fig. S3) In Supp. Fig. 3, we compare each explanatory variable individually with the peak runoff response to rainfall
Reviewer: In Fig. S3 in the Supplement it would be helpful to include the p values for each regression in addition to r values and to exclude a (red) line for those correlations that are not significant.L372-373: The pair of predictor variables with the highest R² value in our multiple linear regression analyses is total summer precipitation and average temperatures during the preceding winter and spring.
Reviewer: More specifically do you mean the best pair of predicator variables ignoring the first-order control variables mentioned in the previous paragraph?L438-441: On the timescale of peak runoff response in Upper Kuparuk (~24 hours), coarse, silty soils with permeabilities around 10 −5 m/s can allow rainfall to infiltrate to depths on the order of tens of centimeters, comparable to the thickness of the active layer, enabling much of the precipitation to be stored in the subsurface
Reviewer: A citation should be provided for this permeability value. While the overlying organic soils in the Kuparuk basis likely have high permeability, the mineral soils are rich in loess and likely behave more like clay-rich soils. Thaw depths as great as cited in line 427 (up to 50 cm) would extend into this loess rich mineral soil. Differences in the hydraulic conductivities of these two materials are substantial (e.g. Hinzman, L. D., D. L. Kane, R. E. Gieck, and K. R. Everett (1991), Hydrologic and thermal properties of the active layer in the Alaskan Arctic, Cold Regions Science and Technology, 19(2), doi:10.1016/0165-232X(91)90001-W.L448-449: These localized pools, due to the high heat capacity of water, can enhance thaw and generate spatial feedback in both storage capacity and runoff routing.
Reviewer: Here and elsewhere, there are statements of fact that are likely to be true but are unsupported by relevant citations.L473: significant
Reviewer: If you use the word "significant" please provide a p value based on a test. Otherwise say "important", "substantive" or similar.L486-488: We hypothesize that it is not the act of stabilization per se that reduces runoff, but rather the gradual thaw and drainage of the exposed ice-rich layer. As the active layer deepens and drains out pore water in the scar zone over time, increasing its capacity to store water.
Reviewer: Is there evidence that the active layer has deepened and dried? Might this also be due to the reestablishment of vegetation and organic layers in the stabilized ALD that begin to insulate the soil in a manner like the undisturbed Goose site?L512: Figure 8.
Reviewer: Perhaps stack panels e and f under c and d in a 3x2 configuration rather than 2x3.L558-559: This implies that rainfall mobilizes DOC and TDS flux at these catchments.
Reviewer: Then why is there no substantial correlation with rainfall described in the previous paragraph (L545-546)? Is there a contradiction here? Or perhaps simply a need to more clearly state that rainfall mobilizes (dislodges) DOC and sediment in place, but runoff is the mechanism responsible for lateral transport of these materials?L583-584: Unfortunately, the sparsity of the available data precludes a clear assessment of differences in runoff response between the periods when the ALDs were active versus stable at Ptarmigan
Reviewer: Given this statement I think any further discussion of what might have happened is entirely speculative. This speculation is not necessarily wrong, but it can't be substantiated and so I think it is best to delete this paragraph.L610-619 in Figure 9: Thawing of the subsurface can increase storage capacity and thus decrease runoff sensitivity to rainfall….etc.
Reviewer: Most of the rest of this lengthy legend repeats interpretation in the narrative of the manuscript and should be deleted here.648-649: they are comparably influential Reviewer:
Replace with "their influence is similar"?L650-651: Interannual variability in runoff response is also significant ( Fig. 4 ), underscoring the need for year-specific predictive modeling.
Reviewer: The intent here is not clear. Interannual variability in runoff response is likely. But if you know the response has changed, why do you need predictive modeling? Perhaps delete this reference to annual predictive modeling here as you take this up again, more cogently, in the final paragraph.Citation: https://doi.org/10.5194/egusphere-2025-4275-RC2
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 176 | 36 | 17 | 229 | 30 | 13 | 15 |
- HTML: 176
- PDF: 36
- XML: 17
- Total: 229
- Supplement: 30
- BibTeX: 13
- EndNote: 15
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
The paper entitled "Characterizing runoff response to rainfall in permafrost catchments and its implications for hydrological and biogeochemical fluxes in a warming climate" utilizes the ensemble rainfall-runoff analysis (ERRA) framework across three permafrost-underlain catchments to understand how rainfall driven runoff varies with biophysical and precipitation. The authors utilize data from the large and well-studied Upper Kuparuk River in Alaska and two very small watersheds in the Canadian high arctic; one of which is impacted by thermokarst.
ERRA is a new method and I will take the approach and framework 'as is' and will not present any criticisms to its methodology. Like a unit hydrograph, it provides a response function of catchments runoff (or other factors) to precipitation inputs, yet can handle nonlinear, non-stationary, autocorrelated and heterogenous systems as outlined an earlier paper that has been published in HESS. As noted, this manuscript seeks to use ERRA for three permafrost underlain watersheds, which are inherently non-linear and heterogeneous, to improve our process understanding and interrogate the influence of phenomenon like active layer detachments.
I read this manuscript several times with considerable interest. There are few people working in cold environments, and applications of new and novel methods are welcome. That said, there is considerable process understanding developed from decades of hard-won observation and careful analysis. As it stands, I do not believe that his paper is suitable for publication in its present form. I have a number of comments that I hope the authors will consider to improve this manuscript to make it more impactful to the permafrost hydrology and catchment science community.
First, and I hesitate to say this, the writing is colloquial and perhaps not up to publication standard. Suggesting improved writing is an easy throw-away comment, but I found it very causal with many interruptions. More detailed comments are below, and I strongly suggest that the authors separate the Results and Discussion to remove speculative comments and to identify where this work sits within the broader and more recent published literature. At times, I was jumping back and forth between what were new results, results that supported the literature (if referenced) and speculation.
Comments by line:
L51. Why ‘seemingly’. Is permafrost not impermeable? Or relatively so? If not, please provide references.
L55. Wang et al. 2021 is referenced twice.
L57. Wolvord & Kurylk is 2016.
L57. Is there a referencing order/format? It seems random here and in other places.
L60. It is likely Koch not Coch et al. 2018
L61. It is likely DeBeer et al. 2016 not De Boer et al. 2016. Neither are in the reference list.
L66. The authors in the previous line discuss rainfall, and here discuss how peak flow and flood response relate to permafrost thaw. Clearly, the expansive permafrost literature indicates that peak flows are most often (although obviously not always) associated with spring snowmelt freshet. Higher peak flows are most likely associated with increased snowfall and/or intense melt along with rain on snow, not summer rainfall. There is literature that discusses this.
L68. I am unsure as to why the ‘peak streamflow’ is discussed here as noted above. Peak streamflow in almost all permafrost rivers is associated with melt, not rainfall, except at potentially very large scales and in certain exceptional years.
L70. This will arise later, but the authors focus on thermokarst as a key process affecting flows. I would like to push back against this. While a startling and important process at local (and even scales up the ~100 km2), thermokarst is not a pan-arctic driver of changes in flows. I’m happy to be proven wrong. There is an observation bias simply because of its dramatic effect, yet it is confined to ice-rich regions, and there are many areas underlain with permafrost that are not influenced by thermokarst. Probably the vast majority of the arctic.
L72. I’m unsure as to the terminology here. ‘granular pore-scale storage capacity’. Is storage capacity not a clear enough term?
L74. Again, ‘pore-scale’ storage capacity? I’m curious as to what other storage capacity would be in play here?
L76. I agree that thermokarst affects runoff at local scales, but is there any supporting literature as it its ubiquity and influence at larger scales? I’m unsure if there is.
L80. There has been considerable ground-based observations in permafrost underlain regions. The Upper Kuparuk River and its sub-basins are some of the most well studied in the world, but the literature citations here are almost 30 years old and neglect much of the newer Alaska North Slope work that looks at runoff, chemical fluxes and seasonal responses. Simple searches, articles by Shorgren, etc., will reveal a wealth of process information not cited but pertinent.
L87. I’m unsure as to what the linkages between remote sensing and process-scale subsurface characteristics are. Is this easy anywhere? Is remote sensing useful in understand rainfall-runoff response in other environments and not permafrost ones? I’m not following this thread.
L91. There are many models that have worked to predict runoff form permafrost environments, many in the past five years that are not referenced. Papers by Rawlins and Painter are just two of many authors to consider.
L92. I agree that we do not fully understand runoff processes in permafrost watersheds, but the statement: “we still do not adequately understand how permeability, hydraulic potentials, and subsurface storage capacity will change with rainfall intensity and contributions from snow/ice melt” is somewhat peculiar. There is a wealth of literature showing how subsurface permeability, transmissivity and flow changes with seasonality and active layer development. As thaw progresses, the classical transmissivity feedback processes occur in permafrost catchments as porous near-surface layers rapidly convey water, yet as thaw progresses and water tables decline, runoff also does. There is almost 30 years of literate on this that is not referenced. While I understand that the Cape Bounty watersheds do not follow this conceptual model well, the Upper Kuparuk certainly does as it was in part developed there. The vertical aspect of water transmission and differences in depth-dependent permeability is important in interpreting the results yet is absent from the manuscript.
L97. I believe that this manuscript is confined to rainfall and should be clearly stated.
L97. This will arise later, but flows in permafrost catchments do not correspond to antecedent wetness – or at least antecedent storage. I believe the authors understand this and should reframe things. For example, in early June, when flows are high, antecedent water storage is very low, although streamflow (defined as wetness?) is very high. At this time, thaw depths are shallow, there is very little available storage for water. Flows are high and rainfall is rapidly transmitted to the stream (along with water released form the thawing active layer). As the seasons progresses, potential storage increases as the active layer expands. Flows can be equivalent in August and June, yet the ‘antecedent storage’ in August would be many times greater than June - with respect to liquid water anyway, but flows may be the same. Antecedent wetness can vary considerably from antecedent discharge, which is likely true in many places but amplified in permafrost environments. This is a clearly established conceptual model from permafrost catchments that is not well addressed in this manuscript.
L106. I’m wondering when the last time unit hydrographs appeared in HESS? A simple search shows only ‘reflective’ articles. While useful for teaching, the unit hydrograph (to my knowledge) is not widely applied in catchment science.
L111. Is “real-world” needed?
L123. “Relatively free” of glacial melt inputs? To my knowledge, there are no glaciers in either of these catchments. In addition, the vast majority of arctic watersheds at the headwater scale are free from glacial influence (and aufeis). While glaciers and incredibly important at larger continental and regional scales, and aufeis is a dynamic source of streamflow in catchments with extensive surface-groundwater interactions, the literature referencing here is somewhat confusing. They are not ubiquitous nor globally important across pan-arctic regions.
L130. Are thermo-erosional features common? They are dramatic and not rare, but ‘common’ is likely untrue. There is literature to cite as to their occurrence and terranes vulnerable to thermokarst that can be cited.
L131. Yokely et al. in review is not in the citations.
L139. The Kuparuk is 139 km2. The Cape Bounty Catchments are 0.18 and 0.21 km2. Nowhere is there a discussion of scale and its influence on the integration of results.
L144. How would a single tipping bucket rain gauge in a very large catchment influence the interpretation of the results? In summer, storms on the North Slope are convective and likely there are events that are missed/mismatched. Does this have any influence on the ERRA or its interpretation?
L145-149. I’m unsure as to the need for this sentence. Likely high frequency measurements are useful everywhere and the historical referencing is somewhat peculiar.
L150. Limited potential water sources? Most catchments receive snow and rain. Active layer thaw provides water certainly, but please consider comments above.
L156. Is it simple?
L158. This is somewhat repetitive from above and could be streamlined with a cleaner site description.
L161. Permafrost thaws, it does not melt.
L172. There is an indication of lower vegetation, although vegetation characteristics of the Upper Kuparuk are not given.
L179. Is there a need to speculate as to why one site had active layer detachments. Such a small slope difference may not be the reason as other simple topographic features like aspect and convergence can be invoked.
L237. The focus is on rainfall. Somewhere the reader needs to understand that this is a small fraction of the total water export from these watersheds. I doubt these are peak flows.
L246. There are 12 predictor variables to related RRD to environmental factors. I am uncertain as to how they were chosen, and there are some concerns I have. Number 1 and 3 appear to be the same. Number 9, 10 and 12 are highly correlated. Is number 11 well captured? I’m curious as to how previous summer rainfall intensity affects current year RRD. In the end, I believe that there should be some rationalizing of these 12 predictor variables. I can think of others from the literature that should be considered such previous season or fall total precipitation.
L252. Calculating total summer precipitation and rainfall as the average of the available data multiplied by the combined three summer months seems problematic, and is certainly an ‘extrapolation’ of reality. I’d like to see some analysis of how this affects analysis with complete data being downgraded and this method used to assess its influence on RRD. I understand that data provision is a challenge, but the influence of this on the interpretation seems to perhaps be large.
L256. Was freshet caught each year? I know this is a challenge.
L274. I do not believe that this analysis evaluates peak runoff. Rainfall driven runoff perhaps. I also do not know why this paragraph appears here.
L283. Separating the results and discussion would help identify the contributions of this manuscript with respect to the published literature.
Figure 2C. This information is a reproduction of 2B and likely not needed. Labelling the ‘potential point of saturation’ is also misleading as there is no empirical evidence for this.
L301. How does 57% compare with the published literature, even for this catchment or others form the North Slope.
Line 302-304. This is hard to contextualize and understand without literature to reference. These are very small numbers. I’m uncertain as to the meaning.
L305. Again, discharge in permafrost catchments is a weak reflection of catchment wetness. I’m not disputing the data, just the process interpretation. Maximum flows (even post freshet) are associated with low antecedent ‘wetness’ in terms of total mm of water available in active storage.
L310. There is considerable literature from the US, Canada, China, Russia and Scandinavia to reference here that is missing, most of which is more recent than a seminal 54 year old paper. The temperate catchment references in my opinion are not appropriate analogues to these catchments.
L315-323. The discussion of water tracks is important, but at the scale of the Upper Kuparuk, there are other issues such as beaded streams and channel routing that need to be considered. There are papers and literature on this. While water tracks are an important feature in this environment, there are other processes that become important as scale increases. In addition, there is no discussion here of depth-dependent hydraulic differences that are well studied and referenced in this environment.
Figure 3. The rainfall intensities are very low, but perhaps this is just how things are presented vis-à-vis a unit hydrograph type approach. It would be nice to understand how these intensities match up with the intensities of arctic storms, which are certainly increasing. Figure 3c suggests that as intensity increases, peak runoff increases along different ‘wetness’ (flow) classes. I’m wondering why the focus on peaks and intensity as opposed to total volumes? Perhaps I am caught a bit up in the weeds here but I’m struggling to understand the implications of this figure. Greater intensity (not total?) precipitation events generate greater NRF across lag times? Does total precipitation matter? Was it analyzed? Probably just a bit of clarity needed.
L345. I’m unsure as to the value of this speculative comment.
Figure 4 is interesting as there is considerable variability, but I am not sure that this is particularly clear to the reader or interpreted correctly. The 12 potential explanatory variables are used to provide a reason for this variability (with some factors having less data than others). Line 369 suggests that total summer precipitation (rainfall) is a fist order control on peak runoff response to rainfall. The variance simply could be because in one year all the rain was in the early season and in another it was all in the late season. The emphasis of interannual differences of event scale metrics can be highly influenced simply by timing. Was this considered?
Also, the discussion relating to snow versus rain is confusing things. Is there much rain below 2 degrees? If so, these values should be clearly presented and this seems more like a repetition of methods.
L373. The average temperature during the preceding winter and spring as a predictor as a key factor controlling RRA seems somewhat peculiar and looking at Figure 5c suggests a very weak relationship. An average winter temperature, in such cold environments, has very little impact on summer thaw and active layer development. There are many decades of work on heat transfer in permafrost soils that would suggest that summer temperature and thew rates far exceed any antecedent winter thermal conditions. The thought that a cold or a warm winter in such extremely cold environments overrides the ‘in season’ climate needs some considerations. There are other factors like previous season or late season precipitation that process studies have used to explain current season responses that make more process sense. This goes to the selection of the 12 factors - which could lean a bit more on the process literature.
L404. Yes, this is well established. Work from across Alaska in different permafrost environments from Caribou-Poker Creek to Toolik Lake based catchments show this. More appropriate referencing to this response that is related to active layer thaw, storage and vertical profiles of conductivity would be welcome.
L412. This is not peak runoff which would likely be during freshet.
L420. The decline has been noted in the literature and is related to active layer development and flow pathways.
L423. There is more recent literature on evapotranspiration in permafrost watersheds and its coupling to runoff response and seasonality. Certainly, they are decoupled, but the process of runoff generation and ET are well documented.
L430. The observation that runoff decreases with season in permafrost catchments is one of the most common observations and should be cited with references more recent than 1998 for Upper Kuparuk.
L434. I disagree with this statement. Antecedent wetness is not a process and its interpretation does not square with process understanding from permafrost watershed research.
L437. I am unsure how vegetation enters the discussion of hydraulic conductivity, and the following discussion of infiltration with respect to soil texture is simply speculative in the face of again, considerable literature. The hypothetical paragraph staring line 444 does not advance our underrating of process.
Another process absent from discussion is one of lateral connectivity, which can be facilitated in permafrost underlain catchments as wetness increases. It is an environment where thresholds dominate. Consider the work of Quinton from the late 90s.
Section 4.5 seems out of place and an add-on to the manuscript. The inclusion of material transport here at one site is a distraction this late in the manuscript. I think a more focussed analysis on rainfall responses across permafrost watersheds would have provided the potential for process insights than data from a very small single site.
Literature on active layer detachments and their influence on runoff and water quality exist for Alaska and the Northwest Territories that should be cited. Undoubtedly ALD will influence runoff response, although I’m struggling to understand how ERRA sheds new light here on what is going on.
L491. There is considerable literature on the geomechanics of active layer detachments. ‘lubricating subsurface layers’ is not particularly technical.
L502. The statement discussing ALD on flash floods and damage critical infrastructure does not make much sense considering the scale of these ALD. More likely, an ALD will simply block a road or destabilize a foundation as mentioned in the cited literature. I’m not sure the alarmism is well founded and the final comment on L506-508 is beyond what can be stated by the analysis here.
L520. Yes, rainfall mobilizes solutes and sediments, but it can also dilute them. The picking and choosing of literature here is peculiar considering an extremely large body of work on water quality and flows at catchments (including the Upper Kuparuk) and the development of conceptual models that are not referenced. Again, see more recent work by Shogren.
L546. While it is acknowledged that material flux is positively associated with discharge (because discharge is in the flow calculation) how can you suggest that this is true as there is no association between discharge and the concentrations or values. I’m uncertain as to the reasoning here.
L560. If you state that the data suggests that rain mobilizes DOC and TDS, how does this square with the line 456 that states that there is no association between rain and the material flux?
In the end, I’m unsure as to what this analysis adds to the already good work of Beel documenting this process at this site. The authors need to emphasize this and also cite work of Bowden, Tank and their team (just two scientists that come to mind).
Figure 9 is similar to other conceptual models in the literature over the past 30 years defining active layer expansion and water/material fluxes. Recent ones by Grewal come to mind and older ones by Quinton from an environment similar to the Upper Kuparuk in Canada. For 9c, d and e, the stream seems far above the slope/riparian zone and is a bit confusing. I’d suggest permafrost not be blue but perhaps grey or a color not immediately associated with water.
L628. The year to year variation in peak runoff being negatively correlated with average temperatures during pervious winter is a weak (panel 5c) and in-season conditions are a much greater proxy on how rapid thaw would be. The degree day models while empirical are pretty good at predicting thaw so I’m a bit surprised. I suggest that the timing of precipitation within the year has much to do with this variability (early v. late). Winter temperatures have warmed much more dramatically across circumpolar regions over the last several decades, yet no appreciable influence on rainfall-runoff processes have been observed form this warming so I struggle to understand causal mechanisms that warm winters facilitate more rapid thaw.
SM Figure 6. It is extremely hard to interpret either the precipitation or temperature.
SM Figure 7. As noted, there is mixed responses between discharge and material/chemical fluxes that confound some of the explanations in the manuscript. DOC is largely chemostatic, perhaps. TDS as well with a bit of dilution, SS flux and POC mobilize a bit at Ptarmigan, but relations are relatively weak.