Review Reports

Round 1

Reviewer 1 Report

This paper provides a significant contribution to use GPR to measure river ice thickness. The dielectric permittivity of river ice is relatively complex under natural conditions but is influenced by its physical properties and inner structure. The manuscript presents an interesting study of the sensitivity of the dielectric permittivity to heterogeneities within river ice. Through original observations, a combination of GPR data as well as ice impurities, porosity, density, and temperature enable us to provide insights on the variability of radar transmission speed and the equivalent dielectric permittivity in river ice. Many of the discussion points in the manuscript is fairly easy to follow, it should be suitable for WATER. However, the authors could do a much better job on analyzing and presenting the data before publishing. Followings suggestions must to modify.

 

1.      In many studies, to increase the accuracy of GPR interpretation results, the radar transmission speed is usually measured by the common center point (CMP), why this method was not used in this study?

2.      When interpretation of ice thickness from GPR, the velocity of freshwater ice (0.17 m/ns) was only used when the actual EM speed cannot be acquired in the field. In this study, the actual ice thickness was already measured in the field, thus the actual radar transmission speed can be calculated by the measured ice thickness, and then use this speed to estimate the ice thickness in other sites.

3.      Most of the content (lines 163-179) in the section method is more like results, but the content (lines 198-257) in the results section is more like method, so I suggest rewriting these two sections.

4.      L109: because ofàbecause

5.      L115-116: ice specimens were sampled by a Kovacs…

6.      L122: delete “which”

7.      L135: The ice forming at the beginning…

8.      L150: ThusàAnd, or delete it.

9.      L172: grounded ice

10.   L175: attributedàthat is attributed

11.   L199-201: delete “the transmission speed of a wave can be determined by the electrical properties of a material. Thus,”

12.   L204: In this expressionàwhere

13.   L221: In these expressions,

14.   L239: What do the x and z directions denote? Horizontal (perpendicular to the ice column) and vertical (along the ice column)?

15.   L259: delete “come from actual measurements”

16.   L261: which of the above-mentioned methods is the radar method?

17.   L318: delete “velocity”

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Ground penetrating radar is a noninvasive geophysical technique that can be used to detect electrical discontinuities in the shallow subsurface, and has been widely used for analyses in the glacier ice, river ice, lake ice and snow. This manuscript studies the variability of radar transmission speed and the equivalent dielectric permittivity in river ice, and investigated the effects of impurities, physical properties (porosity and density), and temperature on the dielectric permittivity of river ice. The research method and results provides a good basis for the application of ground penetrating radar technology in the measurement of river ice thickness. Overall the manuscript is well organized and its presentation is good. However, followings still need to be improved:

1)     Abstract: The abstract structure, the research background was too long, while the total length of the main work, observations, results, and conclusion was somehow short.

2)     Introduction: The current introduction presented the distribution and importance of freshwater ice, and uses of ground penetrating radar to measure snow and ice thickness. But the motivation of your research was missed here, namely, why you did this work, what issues you are intended to resolve.

3)     As you introduced in line 96, you have conducted many survey lines in the field, but you only display one group in this study, how about the results in other survey lines.

4)     Section 2.3 looks like a result than a method.

5)     L284-285: how did you calculate the equivalent and mean dielectric permittivity, respectively? Why could the radar method not provide values for equivalent permittivity?

6)     Since you determined the value of the bulk/equivalent permittivity of ice cover at the studied section, could you please present the real ice thickness distribution along the river section and it temporal change based on your 6-times observations? And how much error could be produced if we directly used the permittivity of pure ice instead?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf