the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 Jan 2025
A new 1500-year-long varve thickness record from Labrador, Canada, uncovers significant insights into large-scale climate variability in the Atlantic
Abstract. Grand Lake, located in Labrador, at the northeastern margin of North America, is a deep lacustrine basin that contains a well-preserved annual laminations record spanning the interval 493 to 2016 CE (1524 years). The chronology of this new varved sequence is established from layer counting of high-resolution images of thin sections. Radiometric dating (137Cs and 14C) validates the reliability of the varve chronology. Varve thickness is significantly correlated (r = 0.38) with the total precipitation recorded at the nearest weather station Goose A. The varve thickness series reveals high values during the 1050–1225 CE period, that is corresponding to the Medieval Climate Anomaly, whereas the 15th–19th centuries, related to the Little Ice Age, shows low values. The teleconnections between several Goose A instrumental data series and some modes of climate variability such as the winter Greenland Blocking (negative North-Atlantic Oscillation) and the significant correlations between our varve thickness record and three other Northern Hemisphere high-resolution proxy records suggest that the Grand Lake record tracks North-Western Atlantic large-scale mode of hydroclimate variability over the past ~1500 years.
Competing interests: Pierre Francus is one of the editors of Climate of the Past
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.- Preprint
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Status: open (until 07 May 2025)
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RC1: 'Comment on egusphere-2025-97', Anonymous Referee #1, 02 Feb 2025
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This paper presents a valuable new hydroclimatic record derived from varved sediments in a deep fjord lake at the western edge of the Atlantic Ocean, offering insights into climate variability over the past 1500 years. The authors emphasize the potential of the GL-13 lamination sequence as a proxy for regional hydroclimate and suggest that their findings align with broader teleconnections, particularly with the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Variability (AMV). While the paper makes important contributions to our understanding of long-term hydroclimatic dynamics, there are several notable gaps in the analysis that warrant further attention. The interpretation of this high-potential record is undervalued.
1. Lack of Seasonality Analysis:
One missing issue is the absence of a detailed evaluation of seasonality within the varve record. The authors assert that the varves are annual in nature, with thicker varves indicating higher precipitation and thinner varves associated with drier periods. However, the seasonal distribution of precipitation within the year (e.g., whether the wetter periods are associated with specific seasons such as winter or summer) is not discussed. Given the potential sensitivity of the region's climate to changes in seasonal patterns, a deeper understanding of seasonality could offer important insights into how different climatic factors may influence precipitation timing and intensity throughout the year. It could have important implications for the interpretation of historical hydroclimatic changes and the impacts of climate variability on local ecosystems.
2. Teleconnection Mechanisms:
I appreciate the attempt to come up with spacial patterns. While the authors suggest that Greenland blocking and NAO plays a central role in modulating precipitation in the study region, they do not provide a comprehensive evaluation of how this teleconnection operates within the context of proxy record. Also the associated time and spacial scale is not considered.
Furthermore, understanding whether the relationship between the record and the pattern is constant across different phases would be valuable for refining the interpretation of the varve record.
3. Implications for Hydroelectricity and Future Climate Trends:
The paper makes a useful connection between past climate variability and potential drivers. Nnoting that the trend of decreasing varve thickness over the past 50 years is consistent with long-term variability, it would be interesting to make the link to climate model output.
4. Further Data Validation and Comparative Analysis:
The paper claims that the GL-13 varve sequence is robust and confirms its annual character over 1523 years. The authors briefly mention similarities between their record and others, but a more in-depth comparative analysis would strengthen the argument that the GL-13 sequence is a reliable proxy for regional hydroclimate and enhances the credibility of their interpretation.
Conclusion:
While this paper presents a valuable new hydroclimatic record and offers interesting insights into long-term hydroclimate variability in eastern North America, it would benefit from a more nuanced discussion of the seasonality of precipitation and a deeper evaluation of the teleconnection mechanisms driving the observed changes in the varve thickness. By addressing these gaps, the authors could provide a more comprehensive understanding of the region's hydroclimatic dynamics and enhance the broader implications of their work, particularly with regard to future climate change and its potential impact.
Citation: https://doi.org/10.5194/egusphere-2025-97-RC1 -
AC1: 'Reply on RC1', Pierre Francus, 24 Feb 2025
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The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-97/egusphere-2025-97-AC1-supplement.pdf
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AC1: 'Reply on RC1', Pierre Francus, 24 Feb 2025
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