the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 26 Feb 2026
A compilation of sea surface temperature anomalies from the Southwest Atlantic during the Common Era: challenges and opportunities to support future research
Abstract. Here, we present a compilation of sea surface temperature (SST) anomalies from the Southwest Atlantic during the Common Era. We aim to highlight the challenges and opportunities in advancing our understanding of regional ocean variability and allow to understand the reasons behind the notable scarcity of such records and explore how we can improve mechanisms to prevent misinterpretation and ensure that these efforts effectively support future research. About 24 records indicated that SST anomalies fluctuated throughout the entire Common Era, with values between (-5.84 to 0.62). The limited availability of high-resolution SST records constrains our ability to fully grasp regional climate dynamics and their broader implications for the global climate system. To address this, it is essential to prioritize acquiring records that minimize coastal influences, thereby providing clearer insights into large-scale oceanic and climatic patterns. Enhancing the representation of currently under-sampled regions is crucial for constructing a more comprehensive picture of Earth’s climate history. However, addressing these gaps involves more than data collection alone. It requires a concerted effort to produce and disseminate SST reconstructions spanning the Common Era, while also raising awareness of their value to the scientific community. Ultimately, such initiatives will enhance our ability to anticipate and respond to future climate change, equipping policymakers and communities with the knowledge necessary to build resilience and adapt to an increasingly dynamic climate system.
- Preprint
(1115 KB) - Metadata XML
-
Supplement
(314 KB) - BibTeX
- EndNote
Status: final response (author comments only)
-
RC1: 'Comment on essd-2026-122', Anonymous Referee #1, 26 Mar 2026
The comment was uploaded in the form of a supplement: https://essd.copernicus.org/preprints/essd-2026-122/essd-2026-122-RC1-supplement.pdfCitation: https://doi.org/
10.5194/essd-2026-122-RC1 -
RC2: 'Comment on essd-2026-122', Anonymous Referee #2, 19 Apr 2026
Review of dos Reis de França et al., A compilation of sea surface temperature anomalies from the Southwest Atlantic during the Common Era: challenges and opportunities to support future research, submitted to ESSD.
Summary of review. With apologies for the lateness of this review: I have substantive requests for revision in all sections of this manuscript.
Specific comments.0. Abstract
l. 11-13. Goal is to "to highlight the challenges and opportunities in advancing our understanding of regional ocean variability and allow to understand the reasons behind the notable scarcity of such records and explore how we can improve mechanisms to prevent misinterpretation and ensure that these efforts effectively support future research".
--> Why is this region of interest and importance?
l. 14-15. Results: "About 24 records indicated that SST anomalies fluctuated throughout the entire Common Era, with values between (-5.84 to 0.62)."
--> Further analysis needs to be performed (see comments below), and then this statement of what has been learned from the dataset can be made more specific.
1. Introduction
l. 38-43: Make a stronger case for the need for southwest Atlantic records.
(1) For available paleoclimate observations, the authors can point out that this scarcity is not resolved in updated curated Common Era paleoclimatic databases (e.g. Evans et al 2026, ESSD, and references to component databases therein).
(2) Most importantly, the authors need to make the case here: what we might learn from southwestern Atlantic paleoceanographic records, perhaps drawing from prior paleoclimatic studies, and from modern physical, chemical and biological oceanographic studies. What are the specific outstanding questions concerning regional ocean and climate change? What is the specific role of the southwestern Atlantic in (l.42) "driving and modulating global ocean and atmospheric circulation patterns"?
(3) What is meant by (l. 43) "...ensuring optimal efficiency" in efforts to address the scarcity of observations in this region?
l. 46-50: Missing from the introduction, but needed: an introduction to the ways in which SST was reconstructed from the various proxy observations made in the gathered sediment cores: MAT, UK'37, Mg/Ca; the uncertainties in the reconstruction of SST from these proxies and in this particular region, especially considering the relatively shallow water depths and regional oceanography from which the sediment cores were retrieved and the potential for the dataset to reflect terrestrial influences such as runoff, erosion, and anthropogenic accelerations of effects; and atmospheric influences on the coastal ocean setting. This will be useful for assessing and expanding results and discussion from analysis of the dataset. Some of the regional oceanographic background is at l. 102-110.
2. Data
l. 49-59: Provide original data source URLs in the main text. Describe the specific criteria, and give the rationale for inclusion of data in the database presented here: proxy observation, region, time coverage, time resolution, chronological control, other ... ? These would be important for replicating the work and for adding to the database in the future.
l. 60-71: exploratory visualization of SST anomalies. In this description of how the data were studied, I think the use of broad time windows and regional integration should be justified from a scientific standpoint. Then it should also be justified by the chronological control (see notes on revisions to Supplementary Material). Because the averaging is over time intervals between 150 and 550 years long, it might be better to use a historical climatology averaged over a larger spatial area and a longer time period as reference period. Instead of "summer" (l. 68), define the months within the year over which the average is performed. The rationale for a seasonal average should be described and sources cited, in the Introduction (see notes on l. 46-50).
l. 74: Fig 2:
(1) Please revise to indicate the differential lengths of the time periods studied: make boxplots the width of the named time periods, and give time in years CE on the horizontal axis in addition to the names. This will help readers unfamiliar with these names to understand the results. It also may provide a discussion point: since most of these names, if not all, originated with studies in the North Atlantic, to what extent does the exploratory visualization assume an Atlantic-wide common temporal expression of SST anomalies? This is not certain to be the case for nearshore/shallow water depth records from the southwest Atlantic (really - Brazil-Argentinian Margin might be a better description of the region sampled).
(2) Fig 2: Because the boxplots indicate nonnormal distributions within time intervals, I suggest you plot medians for each record within each period and boxplot.
l. 67-68: Explain the rationale for comparing the results to tropical global SST anomalies from Abram et al (2016). Background for this rationale should be in the Introduction (see notes on l. 38-43).
l. 69-71: These two sentences seem to be elements of Discussion; please move them there.
3. Results:
l. 73: I suggest creating a section 3, Results, which contains Figs 2-4 and the text describing the results of the analysis of the database.
l. 80-96 and Fig 2: Because the SST reconstructions are from shallow water depths, and from Fig 2 results, I suggest making more robust inference on boxplot medians rather than ranges. This might be also justified by introduction to the uncertainties in creating the SST reconstructions, and estimates of the SST reconstruction uncertainties (l. 46-50).
l. 115 and Fig 4: I think this figure logically comes next, as it addresses the question of whether the Brazil-Argentinian Margin dataset introduced here shows similar Common Era variability as does the Ocean2k compilation of global SST. I think that data should be presented similarly to the boxplots as shown in Fig 2, for reasons that are detailed in the McGregor et al (2015) paper which is cited and sourced for the global mean reconstructed SST comparison. Specifically, all the gathered data for that 2015 paper were on different timescales, resolutions, and nominal chronologies, so were perhaps best considered as binned composites, similar to what is done in Fig 1. This also has the benefit of allowing the authors to make inference on medians and changes in medians between one time period and the next. It looks like the same resolvable features are in both composites: relatively flat in the first millennium, with a cooling in the 1300-1800 period.l. 121-122: "These findings demonstrate that the SW Atlantic lacks adequate records to represent Common Era SST anomaly changes...": This discussion argument seems to be contradicted by the results in Fig 3.
l. 121-122: I understand that the authors argue that it is a change in the relative representation of warm vs cold current influenced regions in the regional SST reconstruction that creates the apparent agreement noted in the prior comment. This needs more support from data analysis. For instance, looking at Fig 1 for core locations, and then Fig 2 and Fig 5, it seems like:
(1) l. 110-112: The authors write: "Notably, the sedimentary
records north of 25°S span 778–2010 CE and are influenced by the Cabo Frio coastal upwelling system, which may amplify the regional SST cooling signal from the LIA to the present (Fig. 5)." The authors seem to be referring to record NAP62-2; other northern records are entirely within the LIA. Yet it seems from Fig 1 that at least 3 other records span this period and are within the current (no pun intended) influence of the warm Brazil Current (Fig 1) during the LIA.(2) Within the Little Ice Age period (Fig 2) there are 10 records available spanning a wide range of color codings. If those color codings are as indicated in Fig 5, then a wide range of sites along the coast, and in the influence of the warm Brazil Current, are sampled.
(3) A comparison between record LaPAS-KF02 spanning nearly the entire time period, and NAP62-2, might indicate whether this is the case. Of course, if the data are composited as anomalies relative to modern means, then the effects of differences in mean SST near the upwelling region and across the transect will be removed from the composite already.
(4) I am unable to further assess the authors' arguments by, for instance, making a plot of mean reconstructed SST vs site latitude, or a composite of selected subsets of the data by latitude, or comparing across subsets by proxy observation, because the authors have only provided a single value for each time point in the compilation in their Figshare repository (l. 150-152), rather than the SST reconstructions by core and providing their associated metadata. Please provide the complete database and all metadata in the repository, such that further exploration of the dataset is possible.
(5) If the authors wish to argue that there has been a shift in SST along part of this transect, which might be related to the global or Atlantic basin SST reconstructions over the Common Era, as composited by McGregor et al (2015): this might be speculated using physical oceanographic arguments and changes in winds in the historical era, but evidence has not been presented to support that idea.
Unfortunately, given these comments (1-4), I find that the authors have not provided convincing support for their argument at l. 112-14, and their conclusion at l. 120-126.
l. 197 and Fig 3: I think this figure lacks rationale and I would differ in my interpretation of the results.
(1) l. 194-196: "Overall, unlike the global trend of rising SSTs observed in several studies, especially highlighting the marked post-industrial warming (e.g., Neukom et al. 2019), the SW Atlantic shows an opposite pattern with a cooling trend from 1850 to 2020 (Fig. 2)." With only a single boxplot in Fig 2 for post-1850 data, this cannot be judged. The results in Fig 3 (blue line) seem to indicate that all values are cold relative to the 1961-1990 mean, and perhaps this is not surprising, as the 1961-1990 period postdates the vast majority of the data in the series. But if anomalies were calculated relative to the 1961-1990 mean, and these remain 2-3 degrees colder than that reference period through the temporal overlap period (Fig 3) - something seems wrong. please check if there might be a mistake in the figure?
(2) Fig 3, time series: how was this constructed? Are there uncertainty estimates on the x and y axes? See also comments on introduction to the reconstructions and apply that information to the revision of this figure. The boxplot composite formulation used in Figs 2 and 4 might usefully enable representation of age and observational uncertainty here.
(3) It's unclear to me why a Southern Hemisphere and global average SST record would be comparable to the SW Atlantic anomaly series, but the legend gives me too little information to understand what is here. Are the SH and GL averages from historical gridded estimates? I don't find Kennedy et al (2019) in the reference list. I don't know how the averages were made. Earlier there was reference to "summer" values; is summer also used for creating these averages?
(4) The scale of variation for the regional composite is a factor of 4x greater. If the imprint of forced climate change locally is roughly the same as on global SST (regress the global SST field on the global SST time series to find out), then is it possible that the unforced variability, for coastal locations in this region, especially for shallow water depths, is more atmospherically and therefore stochastically controlled? In which case you might expect to see what is in the blue line: no change over the historical period and a high level of interannual variability which is overlain by variability associated with changing sampling resolution for the reconstructions.
4. Summary and conclusions
l. 128-137: I can agree with the first 2 sentences. The third is not supported by evidence presently provided in the manuscript, and might be contradicted by evidence that is presented. The fourth could be true but is not supported by data analysis, and is not currently accessible by data and metadata provided with the manuscript, but could be.
l. 138-148: A discussion of the extent to which high resolution offshore sediment records could be obtained in the region would help support conclusions here. The authors could cite recent publications of datasets in the NOAA/NCEI repository (https://www.ncei.noaa.gov/access/paleo-search/), and also publications in ESSD, for instance:
https://doi.org/10.5194/essd-12-2261-2020
https://doi.org/10.5194/essd-12-2579-2020
https://doi.org/10.5194/essd-15-2081-2023
https://doi.org/10.5194/essd-16-1933-2024
https://doi.org/10.5194/essd-2025-812/
https://doi.org/10.5194/essd-18-1185-2026
https://doi.org/10.5194/essd-18-1921-20265. SM:
Table 1: It would be helpful to have columns for 'bottom date' and 'top date' to allow the reader to see which age models might be best constrained by chronological control, which ones include chronological extrapolation (if any); additional information as mentioned previously would be valuable for dataset users.
Supplementary Figure 1: these data are overwhelming from very shallow water depths <150m. Therefore very close to present shoreline. Is there discussion of what this might mean for any interpretation of the results? Yes, there is! But see prior comments for further analysis and interpretation.
6. References:
Please include links to original publicly accessible datasets, if available, and if not, provide the full dataset and all its metadata in the Figshare repository.
Citation: https://doi.org/10.5194/essd-2026-122-RC2
Data sets
SW Atlantic sea surface temperature anomalies J. dos Reis de França et al. https://doi.org/10.5281/zenodo.18392297
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 290 | 163 | 25 | 478 | 67 | 28 | 33 |
- HTML: 290
- PDF: 163
- XML: 25
- Total: 478
- Supplement: 67
- BibTeX: 28
- EndNote: 33
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1