General comments

This paper describes a study relating glacier meltwater with chlorophyll concentrations around Svalbard. The authors use most (if not all) of the relevant bibliography in a study focused on an important theme in these times of rapid warming of the Arctic regions. Their methods combine coupled atmospheric and glacier runoff modeling and, satellite derived ocean data, which are appropriate methods to the spatial scale of the study. They conclude about a positive association between glacier runoff and chlorophyll concentration in 7 out of 14 hydrological regions within ~10 km from the shore. This conclusion is in line with related studies in Greenland and emphasizes the potential role of glacier runoff in stimulating primary production in adjacent coastal areas and it further contributes to the capacity of the scientific community to foresee the impacts of warming on the Arctic and Antarctic marine ecosystems.

The is an excellent and well written paper about an important topic. Therefore, I believe it should be accepted for publication after a minor revision. I made some suggestions directly on the pdf manuscript file which I attach. Please note that these suggestions should not be seen from my side as a necessary condition for paper acceptance.

General comments: 

The manuscript examines summer phytoplankton bloom in the fjords of Svalbard region and its association with glacier meltwater runoff, sea ice and ocean variables- MLD and SST for the period 2003-2013. Satellite derived surface CHL data and model simulation data is used for getting RUNOFF, SEAICE, SST and MLD. The manuscript shows correlation of summer bloom (CHL data) with the model variables. And reports that 50% (7 of 14) hydrological regions of Svalbard showed CHL increase in summer when RUNOFF increases. But the correlation was limited only up to 10 km distance from the coast.  The manuscript suggests that the association can be due to subglacial plume upwelling and estuarine circulation. For other 50% hydrological regions that do not follow the correlation between summer bloom and glacial melt, role of other players, including land terminating glaciers and sea ice, is attributed.

The manuscript also discusses phytoplankton dynamics of the fjords of Svalbard in the productive season from April to August, and compares it with other Arctic fjords. 

One of the purposes of the manuscript is to explore the feasibility of regional scale monitoring of phytoplankton. And it shows that indeed monitoring by satellites can be useful where in-situ monitoring is not possible or data is not available, though satellites have limitations such as cloud cover, sea ice and lack of sub surface overview.

In literature, such studies are mainly reported for Greenland fjords with limited information on Svalbard fjords. Thus, the gaps identified are valid and the manuscript has attempted to fill the gap. 

Limitations:

What could be the reasons for 50% of the fjords not complying with the pattern of increase in CHL with increase in glacial runoff? Though mentioned briefly, this point needs to be dealt in detail.

Other detailed comments are mentioned in the attached PDF file.

General comments:

It has been several years now that the subject of glacial run-off enhancing primary production in adjacent fjords has been a “hot topic” in Arctic marine research. In recent years, there have been many research papers investigating the subject, most of them featuring in situ observations. However, in situ observations are often lacking spatial and temporal resolution which is needed to extrapolate observed patterns. Further, many prior studies on the subject left the question of how far reaching these effects of enhanced primary productivity would be. Would they extend outside of fjord and onto the shelves? Or would the effects be more local? This manuscript if the first I am aware of to address both of those knowledge gaps. While there are many limitations of using satellite data, which the authors have discussed and acknowledged, their effort is truly a first step in resolving the multiple drivers for enhanced primary production in glacially influenced coastal regions and the first to empirically show the limits of run-off derived productivity enhancement. Furthermore, the paper is well written and their conclusions are well reasoned and supported by their analyses and results. This article is an appropriate fit for Biogeosciences, where many of the prior research on the same topic has been published and it will likely be highly cited in the discipline. I recommend this manuscript to be published with minor revisions. See attached document for further comments.