Relative Sea-Level Rise and Potential Submersion Risk for 2100 on 16 Coastal Plains of the Mediterranean Sea

Round 1

Reviewer 1 Report

This paper identifies and analyses coastal plains at risk of submersion in face of sea-level rise by the end of the 21st century in Mediterranean region. This paper appears to be a follow-up of previous studies in the same basin and therefore relies on the same method. In my opinion, the paper presents interesting findings but, in its present form, is not sufficiently sound, novel and sharp to be accepted for publication. In particular, there is some room for improvements in the methods, presentation and discussion. Please find below more specific comments.

Main comments :

• Sea-level projections and their uncertainty. Please find below several comments/concerns:
  
  • it is not totally clear why the authors made the choice of using the IPCC RCP8.5 projections and Rahmstorf (2007), that are now outdated, especially since the released of the SROCC report in 2019. Note that the SROCC report, in particular, reassesses upward the RCP8.5 projections. The authors explain that it is to follow the same method as in previous studies (that they performed) to ease comparison. In my opinion, this is not a sufficient scientific argument. Furthermore, the comparison with previous work is not really discussed later on in the paper;
  • the way IPCC AR5 projections are used is misleading and there seem to be a misunderstanding of what IPCC projections mean in the AR5. The authors claim that 970 mm is the maximum value of the RCP8.5 in 2100 (e.g. l119), but this is not exactly correct.  970 mm corresponds in fact to the upper bound of the likely range; i.e. 66% of the possible future values are between 530 and 970 mm with a best estimate of 740 mm. Hence there is still ~33% chance for sea-level changes to fall out of this range, and in particular, much larger values could possibly be reached (in case of a large Antarctic melting for instance). I would recommend to review these projections and their meaning more carefully;  
  • the authors use the global-mean sea-level, while for regional purposes, there exist methodologies to compute regional sea-level projections (see chapter 13 of the IPCC AR5). Even in the mediterranean basin, where climate models have serious issues (as mentionned by the authors), assumptions can be made to make decent multi-model regional projections (e.g. relying on Altantic projections near Gibraltar). In my opinion, it would be relevant to justify a bit more the use of global-mean instead of regional sea-level projections. For instance, it may be worth mentionning that global and mediterranean sea-level median estimates  are actually very similar;
  • the way uncertainties are estimated is not representative of the full range of uncertainties. Here, the authors only rely on three climate simulations from three different GCMs (somehow arbitrarily chosen) to estimate mediterannean basin SLR-projections uncertainties. Although it is not fully clear to me what these projections considered, I surmise that they only account for thermal expansion contribution (which is what climate models provide), and therefore exclude uncertainties from ice melting contribution. Furthermore, the projections provided by IPCC rely on more than 20 models outputs. It is this thus irrelevant to consider only three models to estimate uncertainties of projections based on many more models.

=> In summary, to make SLR projections more in line with the current litterature and knowledge, I'd recommend to use the best estimate of the SROCC RCP8.5 and consider the likely range as uncertainty. This is more relevant than the current approach used in the paper and justifiable even without considering regional changes. In addition, authors may want to address « a worst case » projection by designing high-end scenarios (see e.g. Hinkel et al., Earth Future, 2019 or Stammer et al., Earth Future, 2019).

• methods for computing flood maps. It’s not clear what methods is used to compute the flood maps. I guess it’s a bathtub approach but this is not quoted anywhere in the paper. Further more, while uncertainties of the different flood drivers (e.g. SLR, land motions, ...) are assessed here and there, they are not reflected in flood maps and land loss estimates. I think this should be computed to enrich the discussion;

• the overall structure and organisation could be improved to make the main results and discussions easier to follow. I think for example that displaying 1 or 2 floop maps (which are currently in the sup. material) in the main text and discussing the flood extent and uncertainty in light of the associated site specific characteristics and challenges would really help the reader to figure out the interest of the study. I think also that section 3.2 would benefit at being merged with site-by-site results described in section 3.1. Finally, it is argued that one of the reason for chosing these different sites is the fact that they have very different characteristics, but in my opinion, these differences are, at the end, not really exploited and put in perspective of the results obtained;

• finally, imprecisions in the writing, issues with figures/tables and typos make the analysis difficult to follow: some acronyms are not defined (e.g. CRT map (?), Table 2, 3 and 4 are cut off, Figure 2 is quoted but does not exist, ...)

Other specific comments :

• L29: remove ")"
• L33-35:  this objective does not reflect (in my opinion), the paper main results and discussions.
• L52 : Toimil et al. [8 only, not 24]=>tsunami are not mentioned (rather mean sea level, mean and extreme wave conditions, storm surges, extreme sea levels, and river discharge)
• L61-62 : please give a reference to support this statement
• L62-63 : please give a reference to support this statement
• L115-117: I don't understand what "... the 2 global models IPCC-AR5 and Rhamstorf" refers to. Please clarify. 
• L121: hydraulic or hydrodynamics?
• 143: please define EO acronym
• 150-165: I don't think that this is really relevant. See the main comments above.
• 141-142. I don't understand how these uncertainties have been used in the flood map.
• L393. is derived ?

Author Response

Reviewer 1 bis see attach for colorured in red reply

This paper identifies and analyses coastal plains at risk of submersion in face of sea-level rise by the end of the 21st century in Mediterranean region. This paper appears to be a follow-up of previous studies in the same basin and therefore relies on the same method. In my opinion, the paper presents interesting findings but, in its present form, is not sufficiently sound, novel and sharp to be accepted for publication. In particular, there is some room for improvements in the methods, presentation and discussion. Please find below more specific comments.

Main comments :

• Sea-level projections and their uncertainty. Please find below several comments/concerns: 
  
  
  • it is not totally clear why the authors made the choice of using the IPCC RCP8.5 projections and Rahmstorf (2007), that are now outdated, especially since the released of the SROCC report in 2019. Note that the SROCC report, in particular, reassesses upward the RCP8.5 projections. The authors explain that it is to follow the same method as in previous studies (that they performed) to ease comparison. In my opinion, this is not a sufficient scientific argument. Furthermore, the comparison with previous work is not really discussed later on in the paper;

Our motivation in the choice of AR5 RCP 8.5 upper limits:

1) our method was widely described in the Paragraph Methods, together with many references, such as Antonioli et al. (2017, QSR i.c. about 5), along with some quotes to which reference is made. The method is the same used in Lambeck et al. (2011).

2) our maps are added to those published by Antonioli et al. (2017). For this reason they must be comparable as methodology, graphics and physical parameters used (sea level projections and geologic vertical movement) especially in light of the fact that between AR5 and SROCC there are unsignificant differences from a topographical point of view, of maximum few centimeters (Table 1 of the manuscript).

3) Why upper limits? On 2013, when AR5 was published, the C02 content in the atmosphere was lower than 290 ppm, then it constantly raised (see figure above), In July 2019 this value was 415 ppm.  For this reason we used the upper limit of 8.5. In Table 1 we highlighted that differences between the AR5 8.5 upper limit,  97 cm, and SROCC 8.5 upper limits, or 110 cm are low differences considering the effects on inundation phenomena. In the scientific practice, there are no rules that impose the choice of a model or another. We could for example have chosen Kopp et al., 2016, Mengel et al 2016., Horton et al 2014 or Bamber et al 2019 (see Table 1). On the contrary, it is fundamental to clear it and provide the reasons (in this case the graphics of the maps compared with Antonioli et al., 2017 at the light of the minimal differences). As shown in Table 1, and Table 3 column M, the upper limits of the aforementioned models are very similar.

4) The SROCC Report The model was presented at the end of 2019 when our manuscript was already written and also maps were already produced (about 4 weeks for each map). However, as aforementioned, differences are very small (see table 1 and new column M of Table 3).

The way IPCC AR5 projections are used is misleading and there seem to be a misunderstanding of what IPCC projections mean in the AR5. The authors claim that 970 mm is the maximum value of the RCP8.5 in 2100 (e.g. l119), but this is not exactly correct.  970 mm corresponds in fact to the upper bound of the likely range; i.e. 66% of the possible future values are between 530 and 970 mm with a best estimate of 740 mm. Hence there is still ~33% chance for sea-level changes to fall out of this range, and in particular, much larger values could possibly be reached (in case of a large Antarctic melting for instance). I would recommend to review these projections and their meaning more carefully;  

We cannot revise the IPCC projections, but we can use the values published in the AR5 report (n° 31 in our references). Table published in 2013 Report AR5 (page 1181 Figure 13.11), quote exactly the values we reported in our study. Reviewer 1 commented that we cannot use the upper limits. Why? It is very important to declare the used model\projections. Note that on Mediterranean sea, and in particular in the Central Mediterranean sea (Italy), geological movements (both isostasy and vertical tectonics) are very significant, and they must be added to IPCC values (e.g. the tide gauge in Venezia provided 24.5 cm of slr in the last 100 years, while in Marseille and Trieste only 13 cm\ 100 years. The great innovation of our work is to add these differences to IPCC projections, that are very important in the Mediterranean Sea, also considering the projections to 2100.

The authors use the global-mean sea-level, while for regional purposes, there exist methodologies to compute regional sea-level projections (see chapter 13 of the IPCC AR5). Even in the mediterranean basin, where climate models have serious issues (as mentionned by the authors), assumptions can be made to make decent multi-model regional projections (e.g. relying on Altantic projections near Gibraltar). In my opinion, it would be relevant to justify a bit more the use of global-mean instead of regional sea-level projections. For instance, it may be worth mentionning that global and mediterranean sea-level median estimates  are actually very similar;

Here the first phrases of the chaper of AR513.6.5 “Regional Relative Sea Level Changes Regional relative sea level change projections can be estimated from a combination of the various contributions to sea level change described above, emerging from the ocean, atmospheric pressure loading and the solid Earth. Over the next few decades, regional relative sea level changes over most parts of the world are likely to be dominated by dynamical changes (mass redistribution and steric components) resulting from natural variability, although exceptions are possible at sites near rapidly melting ice sheets where static effects could become large. However, towards the end of the 21st century, regional patterns in sea level from all other contributions will progressively emerge and eventually dominate over the natural variability”.

No data on Mediterranean sea projections for 2100. Nowhere in the manuscript do we say that the Global and Mediterranean data are very similar. At the time of submission of the paper (3^nd May 2020) there are no projection for 2100 published for the Mediterranean Sea, so we use global projections to which we add the regional coastal movements calculated with great precision.

The way uncertainties are estimated is not representative of the full range of uncertainties. Here, the authors only rely on three climate simulations from three different GCMs (somehow arbitrarily chosen) to estimate mediterannean basin SLR-projections uncertainties. Although it is not fully clear to me what these projections considered, I surmise that they only account for thermal expansion contribution (which is what climate models provide), and therefore exclude uncertainties from ice melting contribution. Furthermore, the projections provided by IPCC rely on more than 20 models outputs. It is this thus irrelevant to consider only three models to estimate uncertainties of projections based on many more models.

The reasons why we choose only three models are documented in the text from line 155 to line 158. However, we confirm that the uncertainties have been calculated at the best of our knowledge using only three different GCMs because these are the only models, among the one present on the CDS, which consider the mediterranean sea directly connected with the Atlantic Ocean and allow exchange of mass and energy. All the other models have a sea-land-mask which closes the Mediterranean sea: it is well known that the data for the Meditarranean sea from those models cannot be used due to the wrong modelization of energy mass exchange (which is actually zero or externally paramtetrized). Conversely the three models used assure that the water income and outcome between the Mediterranean sea and the Atlantic ocean is, at least, considered and they provide physically consistent values. From the sea level data of those models we calculated the mean sea level rise and the associated uncertainties

In summary, to make SLR projections more in line with the current litterature and knowledge, I'd recommend to use the best estimate of the SROCC RCP8.5 and consider the likely range as uncertainty. This is more relevant than the current approach used in the paper and justifiable even without considering regional changes. In addition, authors may want to address « a worst case » projection by designing high-end scenarios (see e.g. Hinkel et al., Earth Future, 2019 or Stammer et al., Earth Future, 2019).

We thanks Reviewer 1 for this advise. Hinkel and Stammer 2019 published on Earth Future. They were published before IPCC SROCC and they did not contain values to use here. We used the following models to build our maps:

1) AR5 RCP 8.5, with very small differences, some centimetres, with respect to SROCC RCP 8.5, as clearly reported in table 1 and table 2 column M;

2)  an high definition Dtm model;

3) vertical geologic movements (both isostasy and tectonics), local values. Note that GIA and tectonic

Methods for computing flood maps. It’s not clear what methods is used to compute the flood maps. I guess it’s a bathtub approach but this is not quoted anywhere in the paper. Further more, while uncertainties of the different flood drivers (e.g. SLR, land motions, ...) are assessed here and there, they are not reflected in flood maps and land loss estimates. I think this should be computed to enrich the discussion;

We thank reviewer 1. We added in the text, Chapter 2. Material and Method some phrases:

Sea-level change along the Mediterranean coast is the sum of eustatic, glaciohydro- isostatic, and tectonic factors. The first is time dependent while the latter two also vary with location, consists to sum the different components of sea level rise in the following main steps: a) the IPCC-AR5 projections (RCP-8.5 upper limits scenarios) or Rahmstorf 2007; b) the long term land vertical movements from geological data; c) the glacio-hydro-isostatic movement (also named GIA); d) by combining eustatic, isostatic and teconic data projected up to 2100, we provided the expected sea-levels at 2100 for the investigated coastal areas  and the expected inland extent of related marine flooding.

Moreover, in Table 3 we clearly describe the sum of the 3 factors (esutatic+isostatic+tectonics) here considered:

column E Slr projection for 2100 using IPCC AR5 upper limit 8.5

Column G Slr projection for 2100 using Rahamstorf 2007

Column H Vertical tectonic rate (always 0)

Column I GIA

Column K total slr IPCC + GIA for 2100

Column L total slr Rahamstorf + GIA for 2100

The overall structure and organisation could be improved to make the main results and discussions easier to follow. I think for example that displaying 1 or 2 floop maps (which are currently in the sup. material) in the main text and discussing the flood extent and uncertainty in light of the associated site specific characteristics and challenges would really help the reader to figure out the interest of the study.

We thank the reviewer 1 we added 3 map in the main text (Map 1 Fertilia, Map 3 Orose, Map 5 Marina di Campo with explicative captions.

I think also that section 3.2 would benefit at being merged with site-by-site results described in section 3.1.

We disagree. We think that new data on tectonics, in particular with respect to Antonioli et al. (2017), most of data remained the same, we added only new data, not site by site.

Finally, it is argued that one of the reason for chosing these different sites is the fact that they have very different characteristics, but in my opinion, these differences are, at the end, not really exploited and put in perspective of the results obtained

Table 4 explains with great detail our choice. We added a sentence to better explain it: A common characteristic of all the areas chosen was that of not having vertical tectonic movements. Now the explanation is:

the choice of study areas was dictated by several factors. The first factor was the tectonic activity; in fact, we chose only tectonically stable areas to eliminate a variable (with consequent error) in the sea-level change equation. As is known for relative sea-level change, the combined results of eustasy, glacio-hydro-isostasy and vertical tectonic motion exhibit considerable spatial variability; the first of these is global and time-dependent, while the latter two vary with location. As shown in Table 4, the coastal areas chosen for our research have very different exposures, maximum fetch, sedimentological material, wave energy flux, and kinds of geomorphology; our choice was precisely due to their great heterogeneity. A common characteristic of all the areas chosen was that of not having vertical tectonic movements

finally, imprecisions in the writing, issues with figures/tables and typos make the analysis difficult to follow: some acronyms are not defined (e.g. CRT map (?), Table 2, 3 and 4 are cut off, Figure 2 is quoted but does not exist, ...)

As regard acronims, the manuscript contains a list of Abbreviations with the explanations, after the paragraph Aknowledgments We also thank rev 1 because the ex Figure 2 was lacking. Now it is reported as Figure 5  in the text. As regard the acronyms CRT we eliminated from ms and changed in 1:5000 scale.

Other specific comments :

• L29: remove ")"

We removed

L33-35:  this objective does not reflect (in my opinion), the paper main results and discussions.

“The 33 objective of this multidisciplinary study is to provide the first maps of sea-level rise scenarios for 2100 for the IPCC RCP 8.5 and Rahmstorf (2007) projections for the above affected coastal zones, which are the locations of touristic resorts, railways, airports and heritage sites”

We desagree with reviewer 1, the 16 maps for sea level scenarios for 2100 are the main result of our manuscript.

L52 : Toimil et al. [8 only, not 24] tsunami are not mentioned (rather mean sea level, mean and extreme wave conditions, storm surges, extreme sea levels, and river discharge)

We cancelled tsunamis

L61-62 : please give a reference to support this statement

L62-63 : please give a reference to support this statement

We do not need to give references for all this surges from Nederlan 1953 up to Katrina 2016: these events were published in newspapers and the discussion is of public domain. Many damages were reported in the sites where they happened.

L115-117: I don't understand what "... the 2 global models IPCC-AR5 and Rhamstorf" refers to. Please clarify. 

It is clarified in the chapter Material and method:  “Particularly the upper limits of IPCC AR-5 RCP 8.5 [31] and Rahmstorf [17] scenarios”

L121: hydraulic or hydrodynamics?

We changed in hydrodynamics

143: please define EO acronym

Probably the Reviewer 1 hasn’t noticed that in the manuscript there is a paragraph called “Abbreviations” (after the Acknowledgments), line 546 EO: Earth Observation.

• 150-165: I don't think that this is really relevant. See the main comments above.

We thank Reviewer but we disagree, it is important to explain well the model and the values used in the manuscript, At the moment, regional Mediterranean projection for 2100 does not exist.

• 141-142. I don't understand how these uncertainties have been used in the flood map.

Table 3 columns K and L

• L393. is derived ?

The question is not clear

Author Response File: Author Response.docx

Reviewer 2 Report

see enclosed pdf file

Comments for author File: Comments.pdf

Author Response

Reviewer  2 see attch for coloured reply

Open Review

(x) I would not like to sign my review report 
( ) I would like to sign my review report 

English language and style

( ) Extensive editing of English language and style required 
(x) Moderate English changes required 
( ) English language and style are fine/minor spell check required 
( ) I don't feel qualified to judge about the English language and style 

Comments and Suggestions for Authors

see enclosed pdf file

Open Review

(x) I would not like to sign my review report 
( ) I would like to sign my review report 

English language and style

( ) Extensive editing of English language and style required 
(x) Moderate English changes required 
( ) English language and style are fine/minor spell check required 
( ) I don't feel qualified to judge about the English language and style 

Comments and Suggestions for Authors

The paper deals with a topical subject like some important environmental and economic consequences of the ongoing climate changes. For that reason, it certainly deserves scientific consideration. However, the reviewer cannot pass over a few perplexities of a conceptual and organizational nature. First of all, although it explicitly refers to previous works and methodologies well fit for predicting the rise of the average level of the Mediterranean sea along some of the most famous and precious (from a tourist and, generally, productive perspective) coasts, the manuscript proves of difficult reading and fruition for users that are not specifically acquainted with the topic. Note that Water is a journal that focuses on broad spectrum water resources research. It would therefore be desirable (also to increase its impact) that the manuscript illustrates at least the bases of the applied methodologies by the introduction and the discussion of indices and algorithms used for evaluating the geomorphologic, tectonic and oceanographic components of the risk.

We added many sentences to the paragraph Methods, and we specified the term GIA, how to calculate it, and how to calculate the vertical tectonic rates. Material and Method we added 2 different phrases:

“Sea-level change along the Mediterranean coast is the sum of eustatic, glaciohydro- isostatic, and tectonic factors. The first is time dependent while the latter two also vary with location, consists to sum the different components of sea level rise in the following main steps: a) the IPCC-AR5 projections (RCP-8.5 upper limits scenarios) or Rahmstorf 2007; b) the long term land vertical movements from geological data; c) the glacio-hydro-isostatic movement (also named GIA); d) by combining eustatic, isostatic and teconic data projected up to 2100, we provided the expected sea-levels at 2100 for the investigated coastal areas  and the expected inland extent of related marine flooding.”

“Vertical tectonic rates were calculated using the MIS 5.5 higstand (125 ka BP) altitude, considering the eustatic altitude in the Mediterranean sea of 6± 2 meters.”

Furthermore (definitely a not negligible detail), it may appear rather hard, for the average Water author and reader, to accept that Mediterranean coastal areas flooding is totally independent of upstream fluvial dynamics and sediment feeding rate. Indeed, the effects of the well-known “coastal erosion” phenomenon are expected to be at least of the same order of magnitude of the tectonic movements (especially in admittedly “stable” regions). Thus, the reviewer recommends on this subject a specific and convincing discussion.

This question is not clear: we writed in the manuscript: ”note that our analysis does not take into account hydrodynamics models, and the contribution of sediment flow from rivers, coastal erosion and possible anthropic defenses may change the estimated extension of the flooded areas”. Coastal erosion is geomorphic process completely different from submergence. While erosion is not irreversible, submersion is considered irreversible. Coastal erosion is short-time effect of sea level rise that depends on very local scale and reversible conditions (river sediment flow rates, presence of defense works, change of coastal currents, etc.). It has nothing to do with an expected sea-rise over than one meter which will certainly lead to the submersion (irreversible phenomenon) of some areas of the world and the Mediterranean sea. The quantitative forecast of the adaptation of the sandy coasts respect the Present sea level rise is very complex. The passive submersion (the one we calculated) gives us an indication of the most vulnerable areas that will have problems for 2100, penetrating the shoreline towards the hinterland. And this is the purpose of our work. Then are the modalities of adaptation of the individual coastal systems which are site-specific. For example, a barrier-lagoon system can respond by submerging (overstepping) or moving the barrier towards the ground (rollover) according to the sea level rise rate, the hydrodynamic conditions, the slope, the availability of sediments and, fundamentally, the urbanization of the barrier itself. The same applies to the beach-dune systems (which have different evolutionary models) or to the bay bottom beaches. All these processes are the subject of specialist studies (for example a recent work published on Geology, Ciarletta et a., 2019 “Mechanism for retreating barriers to autogenically form periodic deposits on continental shelves”) based on morphodynamic modeling, or on analogues present on the platform. Now, in a work that analyzes the sea level rise vulnerability in numerous depressed areas of the Mediterranean sea, we cannot review how they will adapt on a case-by-case basis. We believe that the publication of the 16 maps with the indication of the submergence of some Mediterranean coastal areas (also to increase the Journal impact) is much more important. The complete reply to his question needs may be 16 different papers each one devoted to a well defined areas.

Finally, the manuscript would considerably benefit from a careful grammatical and syntactic revision.

We payed 235 Euro for th English editing of MDPI (certificate number 19370) .

Author Response File: Author Response.docx

Reviewer 3 Report

This is a detailed paper that outlines the results of coastal vulnerability of a variety of low lying coastal sites from around the Mediteranean. The methodology is clearly articulated and I understand why the detailed data set is available as a seperate resource. I would however prefer to see the maps which illustrate which areas are at risk of inundation to be included in the paper. Having them as a separate data set makes it hard to understand what is being discussed.

The text makes frequent reference to Chapters. I assume this means other sections of the paper. Suggest Chapters is changed to Sections.

The text clearly notes that good estimates were produced from Lidar data but the analysis was more limited when other freely data is used. This point should be noted in the conclusions - namely you need high quality data to get an accurate picture of which areas are at risk of inundation by 2100.

Just to note that sentances should not start with  ....Because... Alternatives are noted below in the minor changes that have been suggested.

Line 29 - remove ....)....

Line 47 - change to ... driving the melting of ice and the thermal expansion of the oceans and the...

Line 50 - change to .... two centuries, global sea level....

Line 63 - change to ...due to the melting of continental ice and thermal expansion/steric effects as a consequence of global warming.

Line 180 - change to - Given the.....

Table 3 - Page needs to be landscape rather than portrait and should only take up two pages.

Lines 386 - 455. These describe the local tectonics of a number of sites. It might be better to integrate this material into the relevant site sections in section 3.1 rather than have a seperate section on tectonics. If this approach is adopted then the title of section 3.1 would need to alter.

Line 236 - Change to  .....Since high-resolution...

Line 265 - Change to - The 16 maps produced (......

Line 274 - Not sure what is meant by ...and humid protected areas...., do you mean human protected areas?

Line 290 - Change to - Due to the  

Line 343 - Change to .... as described in section 3.2.

Line 387 - Change to - In this section....

Line 458 - Change to - Since some

Line 498 - Change to -- based on  climatic scenarios,

Line 516 - Change to ...impacting a coastline....

Line 519 - Change to ...cognizant management of the coastal zone 

Author Response

Reviewer 3 see attach for reply in red

Open Review

(x) I would not like to sign my review report 
( ) I would like to sign my review report 

English language and style

( ) Extensive editing of English language and style required 
( ) Moderate English changes required 
(x) English language and style are fine/minor spell check required 
( ) I don't feel qualified to judge about the English language and style 

Comments and Suggestions for Authors

This is a detailed paper that outlines the results of coastal vulnerability of a variety of low lying coastal sites from around the Mediteranean. The methodology is clearly articulated and I understand why the detailed data set is available as a seperate resource. I would however prefer to see the maps which illustrate which areas are at risk of inundation to be included in the paper. Having them as a separate data set makes it hard to understand what is being discussed.

The 16 maps are the main result, but the paper can result of difficult reading if they are all inserted in the paper and not as additional material. We leave to the Editor the choice if add the maps within the paper. At the moment, as requested also by Reviewer 1 bis, we added only 3 maps, as example.

The text makes frequent reference to Chapters. I assume this means other sections of the paper. Suggest Chapters is changed to Sections.

We followed the rules of the journal, so Chapter and not Sections.

The text clearly notes that good estimates were produced from Lidar data but the analysis was more limited when other freely data is used. This point should be noted in the conclusions - namely you need high quality data to get an accurate picture of which areas are at risk of inundation by 2100.

The conclusions clearly report the following sentence:

“all maps were realized with the same methodology, but only 13 out of 16 were elaborated using high-resolution data derived by LiDAR surveys. The remaining three maps (Larnaka in Cyprus; Bastia in France and Kerkennah in Tunisia) were elaborated through data freely released by the Copernicus program with a resolution that did not allow us to map detailed scenarios; however, the land elevation of these areas was a critical factor for the expected sea-level rise for 2100.”

Just to note that sentances should not start with  ....Because... Alternatives are noted below in the minor changes that have been suggested.

We appreciate the advise of Reviewer 3 but this manuscript has been revised by the MDPI English editing service (certificate number 19370), as reported in this revision, so we prefer to leave the MDPI English editing.

 Line 29 - remove ....)....

Done

Line 47 - change to ... driving the melting of ice and the thermal expansion of the oceans and the...

Done

Line 50 - change to .... two centuries, global sea level....

We appreciate the advise of the Reviewer 3, but this manuscript has been edited by MDPI English editing service (certificate number 19370), as reported in this revision, so we prefer to leave the MDPI English editing.

Line 63 - change to ...due to the melting of continental ice and thermal expansion/steric effects as a consequence of global warming.

Done

Line 180 - change to - Given the.....

We appreciate the advise of the Reviewer 3, but this manuscript has been edited by MDPI English editing service (certificate number 19370), as reported in this revision, so we prefer to leave the MDPI English editing.

Table 3 - Page needs to be landscape rather than portrait and should only take up two pages.

We agree, It is due to a technical problem that will be solved by the editorial manager of Water magazine. The journal force to insert tables and figures in the text and sometimes it is not easy.

Lines 386 - 455. These describe the local tectonics of a number of sites. It might be better to integrate this material into the relevant site sections in section 3.1 rather than have a seperate section on tectonics. If this approach is adopted then the title of section 3.1 would need to alter.

In Chapter 3.1 all sites have a description, in Chapter 3.2 we summarized few sites with new tectonic data.

Line 236 - Change to  .....Since high-resolution...

Done

Line 265 - Change to - The 16 maps produced (......

We appreciate the advise of Reviewer 3 but this manuscript has been edited by MDPI English editing service (certificate number 19370), as reported in this revision, so we prefer to leave the MDPI English editing.

Line 274 - Not sure what is meant by ...and humid protected areas...., do you mean human protected areas?

Wetlands

Line 290 - Change to - Due to the  

We appreciate the advise of Reviewer 3 but this manuscript has been  edited by MDPI English editing service (certificate number 19370), as reported in this revision, so we prefer to leave the MDPI English editing.

Line 343 - Change to .... as described in section 3.2.

We appreciate the advise of Reviewer 3 but we follow the editorial rules of the Journal

Line 387 - Change to - In this section....

We appreciate the advise of Reviewer 3 but we follow the editorial rules of the Journal

Line 458 - Change to - Since some

We appreciate the advise of Reviewer 3 but this manuscript has been  edited by MDPI English editing service (certificate number 19370), as reported in this revision, so we prefer to leave the MDPI English editing

Line 498 - Change to -- based on  climatic scenarios,

Done

Line 516 - Change to ...impacting a coastline....

Done

Line 519 - Change to ...cognizant management of the coastal zone 

Done

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

This is my second review of the authors manuscript. I thank the authors for considering some of my comments in the revised version. However, some of the main issues I raised in my previous review have not been really adequately adressed in my opinion. I presume that some of my points were not sufficiently clear nor my recommendations to improve some aspects of the paper; e.g. I did not comment that "the upper limits cannot be used", neither I wrote that the manuscript claimed that "Global and Mediterranean data are very similar". Below, I rephrase the points that I do think are the most important and should be considered more carefully.

• The use of the term "upper limit". I recommend the authors to use "upper limit of the likely range" systematically instead. Why ? Because the "real" SLR upper limit of the RCP8.5 scenario is not actually kown. The currently hot debate on future Antarctic ice-sheet contribution to SLR (especially since the release of Deconto & Pollard, Nature, 2016) illustrates this; basically, given the current knowledge on SLR contributions and driven processes, it is unlikely but possible that under the RCP8.5 scenarios, > 150 cm SLR by the end of the 21st century would be reached. Hence, the 97 cm provided by the AR5 are not the upper limit. Note that the AR5 clearly expresses the interval 53-97 cm as a "likely range" of the RCP8.5 (i.e. 66% to fall within this range), not a full range of uncertainty. 
•  Uncertainty in the Mediteranean sector. I've tried to access the data of the three climate models ACCESS, BCC-CSM1 and NorESM, but I could not find it on CDS. In general, climate models (or GCMs) [it's my field of expertise] provide the thermosteric/ocean dynamic contribution/IB correction SLR contribution. However, they do not include mass contribution for continental glaciers and, antarctic and greenland icesheets, which instead are estimated separately from glaciers/ice-sheets models that use GCM temperatures and precipitations projections as forcings. Thus, although the authors declare the uncertainty sources (and I agree that it is of prime importance to declare the used of model/projections for the sake of transparency) I still believe that the uncertainties in the mediteranean sector as quoted in Table 3 may be strongly underestimated and misleading. So if what I suspects on ACCESS/BCC-CSM-1/NorESM happens to be the case, I'd recommend either to estimate the full range of uncertainty (but that's a lot of additional work) or not to estimate uncertainty at all and then the authors could just assume that they follow the "upper limit of the likely range of the RCP8.5" and that's it. After all, there are no uncertainty estimates for the tectonic rates nor for the GIA in table 3. Furthermore, the uncertainties are not propagated to the flood area. In any case, having a partial estimate of uncertainty (as I suspect it is the case now) is not relevant.
• Note that the actual full range of uncertainty for the global mean sea level by 2100, is rather comprised between ~30 cm and ~200 cm and does not follow a normal probability distribution.  

Author Response

The use of the term "upper limit". I recommend the authors to use "upper limit of the likely range" systematically instead. Why ? Because the "real" SLR upper limit of the RCP8.5 scenario is not actually kown. The currently hot debate on future Antarctic ice-sheet contribution to SLR (especially since the release of Deconto & Pollard, Nature, 2016) illustrates this; basically, given the current knowledge on SLR contributions and driven processes, it is unlikely but possible that under the RCP8.5 scenarios, > 150 cm SLR by the end of the 21st century would be reached. Hence, the 97 cm provided by the AR5 are not the upper limit. Note that the AR5 clearly expresses the interval 53-97 cm as a "likely range" of the RCP8.5 (i.e. 66% to fall within this range), not a full range of uncertainty. 

We thanks for clarification Reviewer 1 we changed throughout the manuscript the words “upper limit” in "upper limit of the likely range"

Uncertainty in the Mediteranean sector. I've tried to access the data of the three climate models ACCESS, BCC-CSM1 and NorESM, but I could not find it on CDS. In general, climate models (or GCMs) [it's my field of expertise] provide the thermosteric/ocean dynamic contribution/IB correction SLR contribution. However, they do not include mass contribution for continental glaciers and, antarctic and greenland icesheets, which instead are estimated separately from glaciers/ice-sheets models that use GCM temperatures and precipitations projections as forcings. Thus, although the authors declare the uncertainty sources (and I agree that it is of prime importance to declare the used of model/projections for the sake of transparency) I still believe that the uncertainties in the mediteranean sector as quoted in Table 3 may be strongly underestimated and misleading. So if what I suspects on ACCESS/BCC-CSM-1/NorESM happens to be the case, I'd recommend either to estimate the full range of uncertainty (but that's a lot of additional work) or not to estimate uncertainty at all and then the authors could just assume that they follow the "upper limit of the likely range of the RCP8.5" and that's it.

We thanks for clarification Reviewer 1, as recommended, we decided to not estimate uncertain and assumed that we follow "upper limit of the likely range of the RCP8.5" . We cancelled all the phrases regarding the uncertain range calculation from the text and from the Figures.

After all, there are no uncertainty estimates for the tectonic rates nor for the GIA in table 3. Furthermore, the uncertainties are not propagated to the flood area. In any case, having a partial estimate of uncertainty (as I suspect it is the case now) is not relevant.

We agree with Reviewer 1.

Note that the actual full range of uncertainty for the global mean sea level by 2100, is rather comprised between ~30 cm and ~200 cm and does not follow a normal probability distribution.  

We agree with Reviewer 1.

Reviewer 2 Report

The authors somehow responded to reviewer's comments. The manuscript underwent a thorough linguistic revision. The recommendation is "accept in present form".

Author Response

The authors somehow responded to reviewer's comments. The manuscript underwent a thorough linguistic revision. The recommendation is "accept in present form".

We thank reviewer 2 for accepting the manuscript in the “present form”

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The manuscript "Relative sea level rise and potential submersion risk for 2100 on 16 coastal plains of the Mediterranean Sea" by Antonioli at all provides an analysis of potential marine submerging for selected coastal plains of the Mediterranean Sea. These analyses are based on RCP 8.5 sea level projections, and on estimates of vertical land movement.

First of all, the quality of the English language is very poor, grammar is terrible, sentences (almost all of them!) are hard to read, and style is not scientific. I know some of these authors to speak better English than this! 

But language aside, the manuscript seems more like a technical report which had to be written within projects mentioned in the manuscript (btw. projects should be acknowledged in scientific papers Acknowledgment section, not praised!) than like a scientific paper. 

In fact, I fail to see the scientific value of this manuscript. What is your hypothesis? What are your findings? What is new in all this? All I see is a sloppy application of one method to data for some random Mediterranean locations. Why these locations? Do they characterize different coastlines, different areas... are these vertical movements part of bigger area movements, or are they something very local? Can any conclusions be drawn about different parts of the Mediterranean (and not just microlocations)? Why are more sea level projection not used?... too much questions, and too little answers. 

And please never end a scientific paper with these kinds of sentences "People should listen to science for the management of their proper near future: listening to science makes time, money and human lives save." This is sentence for stakeholders and newlines, not for scientific paper! 

Reviewer 2 Report

The abstract is not very informative, and it should show some conclusions. There is no need to name all the study regions here; the authors could use the introduction to detail the geographic locations.

The paper reads Ok, although it needs some corrections. I have highlighted some of the uncommon words, long or unclear sentences, etc., but I have not carried out a full correction. The authors should consider revising the English, which is better reviewed by a professional or a native.

The subject is of general interest concerning Climate Change and sea-level rise, and an extensive database, including DEM and GIA, supports it. The authors also provide neotectonic influence which may cause uplift or subsidence, although some study areas are not mentioned in this section, such as Ibiza.

I have not found an explanation of why the authors selected the IPCC (2013) projections (Rahmstorf scenario) instead of any other predictive model. Perhaps this subject should be included in the discussion. Have they considered the new acceleration rates provided by the other mentioned authors?

I find the situation of Cyprus Island unclear.; Is the Island of Cyprus stable or unstable? It looks like several areas are reported as having some neotectonic movements, but in the table, all regions show 0 values for tectonic, vertical displacements.

The discussion shows some aspects which are or should be presented in the methods section, keeping only the relevant cases. The conclusions are a bit weak. Nevertheless, the authors show some relevant data, which is suitable for coastal management in the study sites. The paper is valuable in this sense, although it needs some corrections.

Please find in the attached file some minor corrections.

Comments for author File: Comments.pdf