The sea level time series of Trieste, Molo Sartorio, Italy (1869–2021)

Raicich, Fabio

doi:https://doi.org/10.5194/essd-15-1749-2023

Articles | Volume 15, issue 4

https://doi.org/10.5194/essd-15-1749-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/essd-15-1749-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 4

Data description paper

|

18 Apr 2023

Data description paper |

| 18 Apr 2023

The sea level time series of Trieste, Molo Sartorio, Italy (1869–2021)

Fabio Raicich

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Final revised paper (published on 18 Apr 2023)
Preprint (discussion started on 12 Jan 2023)

Interactive discussion

Status: closed

RC1:
'Comment on essd-2022-454', Marta Marcos, 14 Feb 2023
This work presents an important effort of sea level data recovery from archives from different sources, in combination with already published observations. The author provides a final product of a sea level record spanning over 150 years in Trieste. The manuscript is well documented and organised. Recovered data have been carefully analysed, even providing a list of the main instrument problems together with their dates. I think the manuscript is sound and certainly deserves publication. The data are very valuable for climate studies, as claimed in the manuscript. I have some rather minor comments and typos that I list below:
Page 1: please, clarify the sentence “Mazelle (1909–1917) reported the hourly data for 1905–1911.” What do the years 1909-1917 mean?

Page 1, line 20: remove “and”

Section 2.3: definition and linking among benchmarks are points of major relevance to build a consistent sea level record. The vertical distances between the different benchmarks are listed and represented. However, I miss some information on the horizontal distances among these points. Also, it would be informative to know how the levelling has been performed: which benchmarks are directly connected and how was the levelling carried out, and which benchmarks are intermediate connections. Also, there is no estimate of the levelling error. Is there information that would allow to compute this error, depending on the accuracy of the levelling for example? One way to do this is described in Marcos et al (2011), included in the reference list.

Page 5: “The complete time series of hourly data from 1905 to 2021 obtained in this work is available in Raicich (2022)”. The data set in the reference indicates that the period is 1939-2018
Citation: https://doi.org/10.5194/essd-2022-454-RC1
- AC1: 'Reply on RC1', Fabio Raicich, 16 Mar 2023
  
  Answers to Reviewer 1
  
  First, I would like to thank the reviewer for her comments and remarks that allowed to clarify and correct some points and improve the paper. My responses are preceded by “R:”. The page and line numbers are those of the original manuscript.
  
  I corrected a few typos and updated a reference:
  Page 2, line 23: ‘30’ instead of ‘20’.
  Page 3, line 31 and page 17, Table 2: ‘CsV 53A’ instead of ‘CsV 53’.
  Page 4, lines 5-6: ‘(IGMI, 2009)’ instead of ‘(Zambon, … 2008)’. The relevant reference was inserted at page 13 after line 35.
  Page 9, line 14 (Eq. A16): ‘AZ1869’ instead of ‘IZ1869’.
  Page 14, line 15: ’58-120’ instead of ’59-120’.
  
  Page 1: please, clarify the sentence “Mazelle (1909-1917) reported the hourly data for
  1905-1911.” What do the years 1909-1917 mean?
  R: “Mazelle (1909-1917)” is the reference at page 14, line 8. It includes seven annual reports that contain the data from 1905 to 1911, that were published from 1909 to 1917. In order to avoid confusion, at page 1, lines 36-37, the text was modified as: “The hourly data for 1905-1911 were reported in Mazelle (1909; 1910; 1911; 1912; 1913; 1914; 1917).”, and the collective reference at page 14, line 8, was replaced by the individual items:
  Mazelle, E.: Rapporto annuale dell’Osservatorio Marittimo 1905, Tip. Lloyd Austriaco, Trieste, Austria, 1909.
  Mazelle, E.: Rapporto annuale dell’Osservatorio Marittimo 1906, Tip. Lloyd Austriaco, Trieste, Austria, 1910.
  Mazelle, E.: Rapporto annuale dell’Osservatorio Marittimo 1907, Tip. Lloyd Austriaco, Trieste, Austria, 1911.
  Mazelle, E.: Rapporto annuale dell’Osservatorio Marittimo 1908, Tip. Lloyd Austriaco, Trieste, Austria, 1912.
  Mazelle, E.: Rapporto annuale dell’Osservatorio Marittimo 1909, Tip. Lloyd Austriaco, Trieste, Austria, 1913.
  Mazelle, E.: Rapporto annuale dell’Osservatorio Marittimo 1910, Tip. Lloyd Austriaco, Trieste, Austria, 1914.
  Mazelle, E.: Rapporto annuale dell’Osservatorio Marittimo 1911, Tip. Lloyd Austriaco, Trieste, Austria, 1917.
  
  Page 1, line 20: remove “and”
  R: Done.
  
  Section 2.3: definition and linking among benchmarks are points of major relevance to
  build a consistent sea level record. The vertical distances between the different
  benchmarks are listed and represented. However, I miss some information on the
  horizontal distances among these points. Also, it would be informative to know how the
  levelling has been performed: which benchmarks are directly connected and how was
  the levelling carried out, and which benchmarks are intermediate connections. Also,
  there is no estimate of the levelling error. Is there information that would allow to
  compute this error, depending on the accuracy of the levelling for example? One way to
  do this is described in Marcos et al (2011), included in the reference list.
  R: In our case the consistency of the time series of relative sea level is guaranteed by the known relationships between the tide-gauge zeros, that can all be referred to Zero Molo Sartorio.
  I am afraid that I can provide only part of the information requested by the reviewer.
  The technical details about the levelling surveys of the 19^th century could not be found. With regard to the surveys since 1926, information is not fully public because of restrictions imposed by the Italian Military Geographic Institute, which carried out the surveys.
  As regard to the distances between benchmarks, new pieces of text were inserted as follows.
  Page 3, line 22 (sect. 2.3.1): “… 1876. The horizontal distance between HM 1 and HM 39 was 52 m along the levelling line (MGI, 1885; 1892). …”.
  Page 3, line 33 (sect. 2.3.2): “… (IZ1894). CsO 53 was connected with CsO 52, located 879 m away. Subsequently, the survey involved CsO/CsV 53A, 42 m away from CsO 53, and CsO 54, 26 m away from CsO 53A (IGMI, 1926). ZMS…”.
  Page 4, lines 2-3 (sect. 2.3.2): “… 2000). Both CsO 39 and CP1965 are 6 m away from CsO 39’ (formerly 54). CsV 39 is just above CP1965. The most …”
  
  Page 5: “The complete time series of hourly data from 1905 to 2021 obtained in this
  work is available in Raicich (2022)”. The data set in the reference indicates that the
  period is 1939-2018
  R: The link in Raicich (2022) (page 15, line 1) leads to the web page https://www.seanoe.org/data/00516/62758/, which gives access to two datasets. The first one is for 1869-2021, which includes the hourly data for 1905-2021 and is freely accessible, the second one is for 1939-2018, which is now outdated and only accessible on request. I agree that this might be confusing. Unfortunately, SEANOE’s policy is to keep the older versions. In order to clarify this point, the sentence on page 5, line 4, was rephrased as:
  “The complete time series of hourly data from 1905 to 2021 obtained in this work is included in the data set for 1869-2021 available in Raicich (2022)”.
  
  Citation: https://doi.org/10.5194/essd-2022-454-AC1
RC2:
'Comment on essd-2022-454', Anonymous Referee #2, 12 Mar 2023

This manuscript reports a useful and important recovery of tide gauge data resulting in a very valuable time series that covers the period from 1869 to 2021 in the harbour of Trieste in the North Adriatic Sea. The manuscript is clear and well written. It precisely reports technical details that are very important to understand how different parts of the time series have been joined. The main scientific value of this work is that it extends the formerly available time series (Raicich at al., 2022) beginning in 1905 and it produces a longer time series beginning in 1859.
The manuscript is publishable in its present form.
However, the author might consider adding more information to further increase the interest of this study. My suggestions substantially concern the time behaviour of the trend and whether a recent acceleration can be identified.
The author writes that (Line 11) “a significant acceleration of 0.008±0.004 mm yr-2 was estimated from the inverse-barometer-corrected sea level time series”. This sentence suggests that sea level rate accelerated uniformly in time. Is this the best way of summarizing the changes of sea level rise rate or there is evidence of a change of the trend in the last 3 or 4 decades?
I suggest adding a discussion whether the acceleration of sea level in the last decades (which is supported by satellite altimetry at global scale) is supported also by this regional time series. If we consider 50 years long period (e.g. 1972-2021, 1922-1971, 1872-1921) or 30 years long periods (e.g. 1872-2001, …, 1992-2021) do we see trends gradually increasing or a sharp difference between the last period and the previous ones?

Minor comment: Figure 8: (a) Monthly MSL and (b) Monthly MSL… it seems something is wrong here, likely b) shows annual mean msl (consistently with the text)

Citation: https://doi.org/10.5194/essd-2022-454-RC2
- AC2: 'Reply on RC2', Fabio Raicich, 16 Mar 2023
  
  Answers to Reviewer 2
  
  First, I would like to thank the reviewer for his/her comments and remarks that allowed to clarify and correct some points and improve the paper. My responses are preceded by “R:”. The page and line numbers are those of the original manuscript.
  
  I corrected a few typos and updated a reference:
  Page 2, line 23: ‘30’ instead of ‘20’.
  Page 3, line 31 and page 17, Table 2: ‘CsV 53A’ instead of ‘CsV 53’.
  Page 4, lines 5-6: ‘(IGMI, 2009)’ instead of ‘(Zambon, … 2008)’. The relevant reference was inserted at page 13 after line 35.
  Page 9, line 14 (Eq. A16): ‘AZ1869’ instead of ‘IZ1869’.
  Page 14, line 15: ’58-120’ instead of ’59-120’.
  
  …
  
  However, the author might consider adding more information to further increase the interest of this study. My suggestions substantially concern the time behaviour of the trend and whether a recent acceleration can be identified.
  The author writes that (Line 11) “a significant acceleration of 0.008±0.004 mm yr-2 was estimated from the inverse-barometer-corrected sea level time series”. This sentence suggests that sea level rate accelerated uniformly in time. Is this the best way of summarizing the changes of sea level rise rate or there is evidence of a change of the trend in the last 3 or 4 decades?
  I suggest adding a discussion whether the acceleration of sea level in the last decades (which is supported by satellite altimetry at global scale) is supported also by this regional time series. If we consider 50 years long period (e.g. 1972-2021, 1922-1971, 1872-1921) or 30 years long periods (e.g. 1872-2001, …, 1992-2021) do we see trends gradually increasing or a sharp difference between the last period and the previous ones?
  R: The sentence at page 1, lines 11-12 (in the abstract), does not suggest that the acceleration is uniform, it just summarizes a property of the whole time series. Details are provided in Section 4, where MSL rise rates are also reported, both for the whole time series, namely 1.5 mm/yr, and in the altimetry period, that is 3.0 mm/yr. This answers the question whether a rate change, i.e. acceleration, has been observed recently.
  Because this is a ‘data paper’, I would not like to extend the discussion to scientific issues as the detection of the transition epoch. The main reason is that the transition is more or less smooth depending on the length of the time period used to estimate the trends. Moreover, in the present case, a complication comes from the peculiar behaviour of the Mediterranean sea level between the mid 1960’s and the early 1990’s (see page 6, lines 28-30). Let the trends be estimated in time windows of N years. If we assume that the sea level steadiness started (for instance) in 1965 and ended in 1993, all the trend estimates from [1965-N+1,1965] to [1993,1993+N-1] are affected by the steady sea level. If N = 30, even the latest period is not completely unaffected. Clearly, this is what the observations at Trieste tell us. The point is that a comparison with the global ocean is not straightforward and I think that such an issue deserves a dedicated study which goes beyond the scope of the paper.
  However, to partly address the question, the acceleration was also estimated removing the ‘critical’ period.
  At page 7 after line 22 (end of sect. 4) the following text was added:
  “To assess how the steady sea level period affects the trend and acceleration estimates, we analysed an IB-corrected time series from which the annual means from 1967 to 1995 were removed. As a result, the linear trends are 1.55±0.14 mm yr^-1 for 1869-2021 and 1.56±0.16 mm yr^-1 for 1905-2021, while the accelerations are 0.004±0.005 mm yr^-2 for 1869-2021 and 0.004±0.006 mm yr^-2 for 1905-2021, respectively. In both cases accelerations are statistically not significant at p = 0.05.”
  
  Minor comment: Figure 8: (a) Monthly MSL and (b) Monthly MSL… it seems something is wrong here, likely b) shows annual mean msl (consistently with the text)
  R: Yes, the reviewer is right. The mistake was corrected: “(b) annual” instead of “(b) Monthly”.
  
  Citation: https://doi.org/10.5194/essd-2022-454-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Fabio Raicich on behalf of the Authors (22 Mar 2023) Author's response Author's tracked changes Manuscript

ED: Publish as is (24 Mar 2023) by Alessio Rovere

AR by Fabio Raicich on behalf of the Authors (24 Mar 2023)

Short summary

In the changing climate, long sea level time series are essential for studying the variability of the mean sea level and the occurrence of extreme events on different timescales. This work summarizes the rescue and quality control of the ultra-centennial sea level data set of Trieste, Italy. The whole time series is characterized by a linear trend of about 1.4 mm yr⁻¹, the period corresponding to the altimetry coverage by a trend of about 3.0 mm yr⁻¹, similarly to the global ocean.