Dear authors,

Your revised manuscript was sent for another round of reviews (to the same referees that review your first draft) as both referees suggested major revisions. I've now heard back from one of the referees (see the referee's comments below). Based on this comments, I decided to accept your paper for publication after you make the minor revisions.

Few comments from my side:

The abstract needs rewriting: Please include a sentence at the beginning that states the relevance of your study.

In general, a good abstract is like a 'paper in short' and should contain: an opening sentence on relevance of the study, a sentence on the objectives of the study (research questions), 2-3 sentences on methods (data), 3-5 sentences on results, and 1-2 closing sentences on conclusions and implications of the work. Please try to rewrite the abstract so that it is brought closer to these standards.

Remove the last sentence in the abstract since the data-archive website needs to go in the section on data availability (at the end of the paper).

Best,
Valentina

Dear Authors,

I have edited your abstract to meet the standards of TC. Note that a multi-paragraph abstract is generally not recommended. Please review the edited abstract (below) and revise if necessary. I changed the term 'via break points' to 'stepwise pattern' as I could not really understand what you meant with the former term. Please correct the sentence if the 'stepwise pattern' is not correct or you meant something differently.

I'd still recommend that you ask a colleague who is a native English speaker to proof-read and edit your manuscript before the final submission. Some of the minor copy-editing will be done by TC editorial.

Best,
Valentina

Edited abstract:
Large Arctic river basins experience substantial variability in climatic, landscape and permafrost conditions. However, the processes behind the observed changes at the scale of these basins are relatively poorly understood. While most studies have been focused on the 'Big 6' Arctic rivers – the Ob’, Yenisey, Lena, Mackenzie, Yukon, and Kolymamost - few or no assessments exist for the small and medium-sized river basins, such as Yana and Indigirka River basins. Here, we provide a detailed analysis of streamflow data from 22 hydrological gauges in the Yana and Indigirka River basins with a period of observation ranging from 35 to 79 years up to 2015. These river basins are fully located in the zone of continuous permafrost. Our analysis reveals statistically significant (p <0.05) positive trends in the monthly streamflow timeseries during the autumn-winter period for most of the gauges. The streamflow increases in a stepwise pattern (post 1981) for 17 out of 22 gauges in September (average trend value for the period of record is 58% or 9.8 mm), and 15 out of 22 gauges in October (61% or 2.0 mm). The positive trends are seen in 9 out of 19 rivers which do not freeze in November (54%, 0.4 mm), and 6 out of 17 rivers which do not freeze in December (95%, 0.15 mm). Precipitation is shown to decrease in late winter by down to 15 mm over the observational period. Additionally, about 10 mm of precipitation that used to fall as snow at the beginning of winter now falls as rain. Despite the decrease in winter precipitation, no decrease of streamflow is observed during the spring freshet in May and June in the last 50 years (from 1966); moreover, 5 gauges show an increase of 86% or 12.2 mm in spring floods via an abrupt change in 1987-1993. The changes in spring freshet start date are identified for 10 gauges; the earlier onset in May varies from 4 to 10 days over the observational period. We conclude that warmer temperatures due to climate change are impacting the hydrological regime of these rivers via changes in precipitation type (rain replacing snow). Other factors such as melting of permafrost, glaciers, and aufeis, or changes in groundwater conditions are likely to contribute as well, however, no direct observations of these changes are available. The changes in streamflow can make a significant impact on the ecology of the zone of continuous permafrost, while the increasing freshwater fluxes to the Arctic Ocean can impact the Arctic thermohaline circulation.