Project

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Cold-season climate variability in the Chilean Andes during the past millennium

Applicant De Jong Rixt
Number 131797
Funding scheme Ambizione
Research institution Geographisches Institut Universität Bern
Institution of higher education University of Berne - BE
Main discipline Hydrology, Limnology, Glaciology
Start/End 01.11.2010 - 31.10.2014
Approved amount 469'388.00
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All Disciplines (2)

Discipline
Hydrology, Limnology, Glaciology
Climatology. Atmospherical Chemistry, Aeronomy

Keywords (5)

chrysophyte stomatocysts; Chilean Andes; climate change; Westerlies; scanning in-situ reflectance spectroscopy

Lay Summary (English)

Lead
Lay summary
Few quantitative temperature reconstructions exist for the southern hemisphere covering the past millennium. Since the earth's climate system is controlled by the global energy balance, high-quality data from the southern hemisphere are urgently needed to fully comprehend climate variability and drivers. This project aims to provide two 1000-year long, quantitative, seasonally resolved temperature reconstructions from the Chilean Andes.

Currently much effort is put into answering the question: 'Does the magnitude and rate of 20th Century climate change exceed natural variability over the last millennium? This is important since it provides information on the influence of e.g. anthropogenic forcing of climate, which is highly relevant for the general public and policy makers. However, climatic reconstructions of sufficient quality and resolution are scarce in the Southern Hemisphere. In addition, most climatic proxies are biased towards the warm growing season; reconstructions for the winter season are typically scarce. Recent studies have highlighted though that the amplitude and direction of climate change differs for each season. In addition, it is mostly the seasonal (or shorter) climatic events which have greater environmental and socio-economic impacts. Therefore there is a particularly strong need for data representing seasonally resolved temperature variability for the Southern Hemisphere.

This project aims to develop two high-resolution, quantitative reconstructions of summer and winter temperature variability in the Chilean Andes during the past 1000 years based on novel methods; chrysophyte stomatocyst analysis and scanning in-situ reflectance spectrometry. A spatial training set will be developed for chrysophyte stomatocysts, based on ca. 50 lakes spaced along an altitude gradient, to allow for high-quality, quantitative winter temperature reconstructions.

The selected study area, the 'Region de Araucanía' (~37-40° S) is ideally situated to reconstruct past changes in the position and strength of the Westerly Wind Belt, which is the most important climatic driver south of ca 38° S in the Southern Hemisphere. This study will provide reconstructions of seasonal contrasts and extremes for two study sites, thus allowing for an assessment of past changes in these Westerlies. These reconstructions will also be used to put recent climatic changes in a long-term context. The temperature reconstructions will also be compared to Global Circulation Model (GCM) ensemble runs, which will provide important clues on natural and anthropogenic forcing factors.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Late Holocene summer temperatures in the central Andes reconstructed from the sediments of high-elevation Laguna Chepical, Chile (32 S)
R. de Jong L. von Gunten A. Maldonado and M. Grosjean (2013), Late Holocene summer temperatures in the central Andes reconstructed from the sediments of high-elevation Laguna Chepical, Chile (32 S), in Climate of the Past, 9, 1921-1932.

Collaboration

Group / person Country
Types of collaboration
EULA Concepcion Chile (South America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
12th International Palaeolimnology Symposium Talk given at a conference Quantitative temperature reconstructions from high altitude lakes, Switzerland and Chile 21.08.2012 Glasgow, UK, Great Britain and Northern Ireland De Jong Rixt;
XVIII INQUA Congress Poster Seasonally explicit climate reconstructions from lakes in the Chilean Andes 21.07.2011 Bern, Switzerland, Switzerland De Jong Rixt;
IGBP-PAGES second International Symposium Talk given at a conference Seasonally resolved temperature reconstructions from L. Chepical, Chilean Andes 27.11.2010 Valdivia, Chile De Jong Rixt;


Associated projects

Number Title Start Funding scheme
113059 SILS "Stomatocysts in Lake Sediments: a novel tool for high-resolution quantitative climate reconstruction" /Environmental Scanning Electron Microscope ESEM 01.08.2006 R'EQUIP
154802 Detection of human and natural influences on the climate system: regional insights from the past Millennium 01.05.2015 Ambizione

Abstract

Currently, large efforts are put into climatic reconstructions covering the past millennium at a high (annual to near-annual) temporal resolution. This type of studies is of crucial importance since it allows researchers to put recent climatic changes in a long-term context. However, the majority of high-resolution studies are based in the Northern Hemisphere. An additional problem is the seasonal bias of proxies; most natural proxies record variability during the warm growing season. Since climatic forcing factors such as volcanic eruptions, solar irradiance and greenhouse gas forcing act globally but may trigger responses that differ depending on the season and location, there is a particularly strong need for high-resolution, cold-season climatic reconstructions from the Southern Hemisphere. This research project aims to provide detailed (near-annual; last 200 years, decadal; last 1000 years), quantitative cold-season temperature reconstructions for two sites in central-southern Chile covering the last 1000 years. With these records, research topics concerning e.g. recent climate change in a long-term context, seasonality or large-scale climatic processes in South America will be addressed. Cold-season temperatures will be reconstructed using chrysophyte stomatocysts, siliceous cysts produced by the so-called ’golden algae’. Chrysophyte cysts are a novel proxy, and previous work has shown the sensitivity of these -primarily planktonic- algae to cold-season air temperatures. This proposal aims to develop a chrysophyte training-set based on sediment trap samples collected during one year, from 40-45 lakes along a long (ca. 3000 m) altitudinal gradient. The Transfer Functions generated by this method will be applied to two high-resolution chrysophyte cyst records covering the past 1000 years to reconstruct cold-season temperatures quantitatively. Summer temperatures will be reconstructed from the same cores (based on scanning in-situ spectrometry at 380-730 nm; VIS-RS) to give insight in past seasonality changes. The VIS-RS scanning methodology will also be tested on surface sediment samples for the training set lakes and compared to conventional methods (e.g. XRD, HPLC, C/N). All results will be compared to climate model-data to study the influence of large-scale atmospheric processes related to e.g. ENSO or PDO (El Niño Southern Oscillation, Pacific Decadal Oscillation) and AAO (Antarctic Oscillation).
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