6 research outputs found
The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period
Quaternary records provide an opportunity to examine the nature of the
vegetation and fire responses to rapid past climate changes comparable in
velocity and magnitude to those expected in the 21st-century. The best
documented examples of rapid climate change in the past are the warming events
associated with the Dansgaard–Oeschger (D–O) cycles during the last glacial
period, which were sufficiently large to have had a potential feedback through
changes in albedo and greenhouse gas emissions on climate. Previous
reconstructions of vegetation and fire changes during the D–O cycles used
independently constructed age models, making it difficult to compare the
changes between different sites and regions. Here, we present the ACER (Abrupt
Climate Changes and Environmental Responses) global database, which includes
93 pollen records from the last glacial period (73–15 ka) with a temporal
resolution better than 1000 years, 32 of which also provide charcoal records.
A harmonized and consistent chronology based on radiometric dating (14C,
234U∕230Th, optically stimulated luminescence (OSL), 40Ar∕39Ar-dated tephra
layers) has been constructed for 86 of these records, although in some cases
additional information was derived using common control points based on event
stratigraphy. The ACER database compiles metadata including geospatial and
dating information, pollen and charcoal counts, and pollen percentages of the
characteristic biomes and is archived in Microsoft AccessTM at
https://doi.org/10.1594/PANGAEA.870867
A three-year Analysis of the Biomass Burning Season in Southeast Mexico by Using a Contextual Fire Detection Algorithm
Abstract A three-year analysis of the biomass burning season in southeast Mexico and northern Guatemala, by far the region with most burning in Central America, is presented in this study. We use a contextual algorithm implemented in our group three years ago. The algorithm is based in Justice (1996) originally developed to be used with AVHRR data, but we readapted it to work with GOES data. Even though some spatial resolution is lost when we use GOES data in comparison with AVHRR, a large increment on time resolution is gained. This permits to detect on-time and continuously monitor fires in a given area, which is quite useful for environmental and civil protection government institutions. The algorithm (called here ADFA) has been monitoring fires in the study area since 2003 during the biomass burning season (approximately from March to May). The results indicate that this year biomass burning season was the most active of the three years. On the other hand, the main of sources of burning also varied from year to year. In 2003 the main burning sources were located in north-western Guatemala, and the peak was found in April; while for 2004, the main burning sources were located in middle Chiapas (Mexico) during April that year; finally, 2005 was somewhat similar to 2003, but the main sources in Guatemala moved a little bit to the south compared to that year
BINCOR: An R package for Estimating the Correlation between Two Unevenly Spaced Time Series
This paper presents a computational program named BINCOR (BINned CORrelation)
for estimating the correlation between two unevenly spaced time series. This program is also
applicable to the situation of two evenly spaced time series not on the same time grid. BINCOR is
based on a novel estimation approach proposed by Mudelsee (2010) for estimating the correlation
between two climate time series with different timescales. The idea is that autocorrelation (e.g. an
AR1 process) means that memory enables values obtained on different time points to be correlated.
Binned correlation is performed by resampling the time series under study into time bins on a
regular grid, assigning the mean values of the variable under scrutiny within those bins. We present
two examples of our BINCOR package with real data: instrumental and paleoclimatic time series.
In both applications BINCOR works properly in detecting well-established relationships between
the climate records compared
Pronounced northward shift of the westerlies during MIS 17 leading to the strong 100-kyr ice age cycles
The MIS 17 interglacial, similar to 715-675 ka, marks the end of the Mid-Pleistocene Transition as intensified, long and asymmetrical 100-kyr ice age cycles became eminently established. Increasing arrival of moisture to the Northern Hemisphere high latitudes, resulting from the northwestward migration of the Subpolar Front and the intensification of the Norwegian Greenland Seas (NGS) convection, has been put forward to explain the emergence of this quasi-periodic 100-kyr cycle. However, testing this hypothesis is problematic with the available North Atlantic precipitation data. Here we present new pollen-based quantitative seasonal climate reconstructions from the southwestern Iberian margin that track changes in the position and intensity of the westerlies. Our data compared to changes in North Atlantic deep and surface water conditions show that MIS 17 interglacial was marked by three major changes in the direction and strength of the westerlies tightly linked to oceanographic changes. In particular, we report here for the first time a drastic two-steps northward shift of the westerlies centered at similar to 693 ka that ended up with the sustained precipitation over southern European. This atmospheric reorganization was associated with northwestward migration of the Subpolar Front, strengthening of the NGS deep water formation and cooling of the western North Atlantic region. This finding points to the substantial arrival of moisture to the Northern Hemisphere high latitudes at the time of the decrease in summer energy and insolation contributing to the establishment of strong 100-kyr cycles. (C) 2019 Elsevier B.V. All rights reserved.Basque GovernmentBasque Government [POS_2015_1_0006]FCTPortuguese Foundation for Science and Technology [PTDC/MAR-PRO/3396/2014, UID/Multi/04326/2013, SFRH/BPD/96960/2013, SFRH/BPD/108600/2015
The ACER pollen and charcoal database: A global resource to document vegetation and fire response to abrupt climate changes during the last glacial period
Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard–Oeschger (D–O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on climate. Previous reconstructions of vegetation and fire changes during the D–O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here, we present the ACER (Abrupt Climate Changes and Environmental Responses) global database, which includes 93 pollen records from the last glacial period (73–15 ka) with a temporal resolution better than 1000 years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (14C, 234U∕230Th, optically stimulated luminescence (OSL), 40Ar∕39Ar-dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on event stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts, and pollen percentages of the characteristic biomes and is archived in Microsoft AccessTM at https://doi.org/10.1594/PANGAEA.870867