Climate in the Iberian Peninsula is impacted by both internal and external climate
modes, which are expected to shift in position and intensity due to anthropogenic climate change. Examples of such modes include the North Atlantic Oscillation (NAO) and the East Atlantic mode (EA). Changes in the behavior in these regional climate modes could significantly alter water availability in the Iberian Peninsula, a region identified by model projections as particularly sensitive to future warming scenarios. There has been extensive research and paleoclimate reconstructions of the NAO and its impacts on Iberian climate. However, to date few paleoclimate records have been developed to evaluate the behavior of the EA over the late Holocene and into the present. The development of highly resolved regional paleoclimate records from Iberia is critical for improving the predictive capability of regional climate models under future warming scenarios and to determine the extent to which different teleconnection patterns are influencing climate. Here we present a near annually resolved stable carbon isotope (δ13C) and oxygen (δ18O) isotope time-series from three stalagmites from the Algarve region of southern Portugal from two caves within 2.3 km of each other. The southern coast of Portugal offers an ideal location to study the behavior of the EA due to the modulation of storm tracks coming across the North Atlantic Ocean into Iberia associated with the EA. U/Th dating indicates that our composite record spans the last millennia continuously through 2018 CE. Two stalagmites (GIA-19-1 and C-18-1) stopped growing around 1600 CE, during a dry interval, and sample GIA-19-2 grew continuously since the 15th century. GIA-19-2, with sub-annual resolution, is compared to modern instrumental records to evaluate the influence of specific environmental controls, including temperature and precipitation amounts. Isotope data from all three stalagmites exhibit substantial multidecadal variability indicating relatively wet and dry intervals. Based on our initial results, it is likely that both temperature and precipitation amount effects are the dominant controls on isotopic variability in these stalagmites. Comparison of the GIA-19-2 oxygen isotope time-series with the instrumental index (1950 to present) and reconstructed index (1650 CE to present) of the EA mode shows strong coherence with both index records. Hence, multidecadal variability observed in our stalagmite isotope time series may provide insight into the historical behavior of the EA mode and its resulting impacts on southern Portuguese climate.
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Climate indices in historical climate reconstructions: A global state-of-the-art.
Abstract. Narrative evidence contained within historical
documents and inscriptions provides an important record of
climate variability for periods prior to the onset of systematic
meteorological data collection. A common approach used by
historical climatologists to convert such qualitative information
into continuous quantitative proxy data is through the
generation of ordinal-scale climate indices. There is, however,
considerable variability in the types of phenomena reconstructed
using an index approach and the practice of index
development in different parts of the world. This review, written
by members of the PAGES (Past Global Changes) CRIAS
working group – a collective of climate historians and historical
climatologists researching Climate Reconstructions
and Impacts from the Archives of Societies – provides the
first global synthesis of the use of the index approach in
climate reconstruction. We begin by summarising the range
of studies that have used indices for climate reconstruction
across six continents (Europe, Asia, Africa, the Americas,
and Australia) as well as the world’s oceans. We then outline
the different methods by which indices are developed in
each of these regions, including a discussion of the processes
adopted to verify and calibrate index series, and the measures
used to express confidence and uncertainty. We conclude
with a series of recommendations to guide the development
of future index-based climate reconstructions to maximise
their effectiveness for use by climate modellers and in
multiproxy climate reconstructions.
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- Award ID(s):
- 1854511
- NSF-PAR ID:
- 10282963
- Date Published:
- Journal Name:
- Climate of the past
- Volume:
- 17
- ISSN:
- 1814-9324
- Page Range / eLocation ID:
- 127301314
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/doi.org/10.5194/cp-17-1273-2021
