Holocene climatic variations in the Western Cordillera of Colombia: a multiproxy high-resolution record unravels the dual influence of ENSO and ITCZ
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2016-11-24
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Abstract
The Páramo de Frontino (3460 m elevation) in Colombia is located approximately halfway between the
Pacific and Atlantic oceans. It contains a 17 kyr long, stratigraphically continuous sedimentary sequence
dated by 30 AMS 14C ages. Our study covers the last 11,500 cal yr and focuses on the biotic (pollen) and
abiotic (microfluorescence-X or mXRF) components of this high mountain ecosystem. The pollen record
provides a proxy for temperature and humidity with a resolution of 20e35 yr, and mXRF of Ti and Fe is a
proxy for rainfall with a sub-annual (ca. 6-month) resolution.
Temperature and humidity display rapid and significant changes over the Holocene. The rapid transition
from a cold (mean annual temperature (MAT) 3.5 C lower than today) and wet Younger Dryas to a
warm and dry early Holocene is dated at 11,410 cal yr BP. During the Holocene, MAT varied from ca. 2.5 C
below to 3.5 above present-day temperature. Warm periods (11,410e10,700, 9700e6900, 4000
e2400 cal yr BP) were separated by colder intervals. The last 2.4 kyr of the record is affected by human
impact. The Holocene remained dry until 7500 cal yr BP. Then, precipitations increased to reach a
maximum between 5000 and 4500 cal yr BP. A rapid decrease occurred until 3500 cal yr BP and the late
Holocene was dry. Spectral analysis of mXRF data show rainfall cyclicity at millennial scale throughout the
Holocene, and at centennial down to ENSO scale in more specific time intervals. The highest rainfall
intervals correlate with the highest activity of ENSO. Variability in solar output is possibly the main cause
for this millennial to decadal cyclicity. We interpret ENSO and ITCZ as the main climate change-driving
mechanisms in Frontino. Comparison with high-resolution XRF data from the Caribbean Cariaco Basin (a
proxy for rainfall in the coastal Venezuelian cordilleras) demonstrates that climate in Frontino was
Pacific-driven (ENSO-dominated) during the YD and early Holocene, whereas it was Atlantic-driven in
Cariaco (ITCZ-dominated). From ca. 8000 cal yr BP, climate in both areas was under the dual influence of
ENSO and ITCZ, thereby showing existing teleconnections between the tropical Pacific and Atlantic
oceans.
The Frontino record is to date the highest-resolution Holocene study in NW Colombia. An implication
of these results is that new records should be analyzed with multiproxy tools, in particular those
providing high resolution time series, such as mXRF.
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