Abstract
This paper evaluates the relationship between fire occurrence (number and burned area) and climate variability (precipitation and maximum temperatures) across central and south‐central Chile ...(32°–43° S) during recent decades (1976–2013). This region sustains the largest proportion of the Chilean population, contains ecologically important remnants of endemic ecosystems, the largest extension of forest exotic plantations, and concentrates most of the fire activity in the country. Fire activity in central Chile was mainly associated with above‐average precipitation during winter of the previous year and with dry conditions during spring to summer. The later association was particularly strong in the southern, wetter part of the study region. Maximum temperature had a positive significant relationship with burned area across the study region, with stronger correlations toward the south. Fires in central Chile were significantly related to El Niño–Southern Oscillation, through rainfall anomalies during the year previous to the fire season. The Antarctic Oscillation during winter through summer was positively related to fires across the study area due to drier/warmer conditions associated with the positive polarity of this oscillation. Climate change projections for the region reveal an all‐season decrease in precipitation and increases in temperature, that may likely result in an increment of the occurrence and the area affected by fires, as it has been observed during a multi‐year drought afflicting central Chile since 2010.
Evolution of heatwaves in Chile since 1980 González-Reyes, Álvaro; Jacques-Coper, Martín; Bravo, Claudio ...
Weather and climate extremes,
September 2023, 2023-09-00, 2023-09-01, Letnik:
41
Journal Article
Recenzirano
Odprti dostop
Heatwaves (HWs) are highly dangerous threats to human and ecosystem health, as well as to many economic sectors around the world. In the present work focused on Chile, we use a high-resolution ...(∼5 km) gridded product (CR2Met v2.0) to evaluate the spatiotemporal distribution and trends of HWs. We analyze daily maximum temperatures (Tx) from late austral spring to early autumn (November to March) to evaluate the HWs behavior during 1980–2020, using three criteria: i) three consecutive days with Tx > 30°C, ii) three consecutive days with Tx > 90th percentile (P90), and iii) three consecutive days with Tx > 95th percentile (P95). We validated our results using HWs statistics based on eighteen official meteorological stations; this procedure revealed a coherence with gridded data mainly over the Central Valley and the Andes. Using the P90 threshold, we found upward trends across the Andes between 20° and 36°S (>1 events per decade), and in the Central Valley between 34° - 43°S (>0.75 events per decade). In addition, using the P90 and P95 thresholds, HWs exhibit upward trends (>1 and 0.5 events per decade, respectively) throughout most of Chile, including Andes and Patagonia. Moreover, using all thresholds, we found an increase in HW frequency during the 2011–2020 megadrought period (ranging from 1 to 4 HWs events/decade) in comparison to the previous period (1980–2010). Meteorological factors such as an increase in the frequency of Puelche (Föhn-like) winds are proposed as an amplifying mechanism of HWs in South-Central Chile.
•Heatwaves in Chile show an upward frequency trend from 1980 onwards.•Upward trends in heatwave frequency are located along the Andes (∼20°-25°S) and along the Central Valley (33°-41°S).•During 2011–2020, on average 1 to 4 more heatwaves per decade were recorded in comparison with 1980–2010.•The increasing heatwaves trend between 38° and 40°S is associated with the increasing trend of Puelche (Foehn-like) winds.
Since 2010, central Chile has experienced a protracted megadrought with annual precipitation deficits ranging from 25 % to 70 %. An intensification of drought propagation has been attributed to the ...effect of cumulative precipitation deficits linked to catchment memory. Yet, the influence of water extractions on drought intensification is still unclear. Our study assesses climate and water use effects on streamflow reductions during a high-human-influence period (1988-2020) in four major agricultural basins. We performed this attribution by contrasting observed streamflow (driven by climate and water use) with near-natural streamflow simulations (driven mainly by climate) representing what would have occurred without water extractions. Near-natural streamflow estimations were obtained from rainfall-runoff models trained over a reference period with low human intervention (1960-1988). Annual and seasonal streamflow reductions were examined before and after the megadrought onset, and hydrological drought events were characterized for the complete evaluation period in terms of their frequency, duration, and intensity.
State-of-the-art climate models project droughts of stronger intensity and longer persistence in many arid and semi-arid regions such as northern Patagonia, which constitutes a serious concern ...worldwide. Moisture availability has a significant influence on the dynamic, stability and function of terrestrial ecosystems. In this study, we used wood samples from 260 Austrocedrus chilensis trees growing in northwestern Patagonia to reconstruct the Standardized Precipitation Evapotranspiration Index (SPEI) for the last millennium (1055–2014). Our reconstruction explained 41.6% of the variance contained in the November–December SPEI at a 1-month scale for the period 1930–2013. The SPEI reconstruction has provided a long record of extreme pluvial (1060s, 1090s, 1200s, 1300s, 1360s, 1390s, 1400s, 1550s, 1580s, 1580s, 1630s, 1940s, 1960s, and 2000s) and drought events (1070s, 1150s, 1170s, 1180s, 1270s, 1310s, 1430s, 1450s, 1570s, 1600s, 1620s, and 1950s) for northwest Argentine Patagonia. Although the SPEI reconstruction indicates that the frequency of extreme events has increased since 1950, our record indicates that current levels have not exceeded those previously reached, particularly when compared to those recorded around the suggested periods for the Medieval Warm and towards the end of the Little Ice Age. The spatial and temporal relationships associated with the South Annular Mode and the Pacific Sea Surface Temperature variability as expressed by the Tripole Index indicated that the temporal variability observed in the SPEI reconstruction is modulated by hemispheric-scale atmospheric circulation dynamics. These climate forcings are likely responsible for the intensity and the rate of occurrence of extreme weather events in northwestern Patagonia. Furthermore, the SPEI reconstruction showed a spatial and temporal pattern similar to that observed in previous PDSI-based reconstructions. This study provides robust evidence of hydroclimatic variations for extratropical sectors of South America, improving our knowledge of the climate dynamics during the last millennium and allowing us to review the recently observed increase in wet and dry events in a long-term historical context.
•A tree-ring-based SPEI reconstruction since 1055 CE was developed.•Dry/wet hydroclimatic extremes lasting several decades were identified throughout the entire reconstructed period.•Middle and high latitude atmospheric circulation dynamics play a key role in hydroclimatic variability.•Wet years are related to the El Niño phase.•SPEI reconstruction showed a spatial and temporal pattern similar to that observed in previous reconstructions.
Spatio-temporal patterns of climatic variability have effects on the environmental conditions of a given land territory and consequently determine the evolution of its productive activities. One of ...the most direct ways to evaluate this relationship is to measure the condition of the vegetation cover and land-use information. In southernmost South America there is a limited number of long-term studies on these matters, an incomplete network of weather stations and almost no database on ecosystems productivity. In the present work, we characterized the climate variability of the Magellan Region, southernmost Chilean Patagonia, for the last 34 years, studying key variables associated with one of its main economic sectors, sheep production, and evaluating the effect of extreme weather events on ecosystem productivity and sheep production. Our results show a marked multi-decadal character of the climatic variables, with a trend to more arid conditions for the last 8 years, together with an increase in the frequency of extreme weather events. Significant percentages of aboveground net primary productivity (ANPP) variance is explained by high precipitation, mesic temperatures, and low evapotranspiration. These conditions are, however, spatially distributed in the transition zone between deciduous forests and steppe and do not represent a general pattern for the entire region. Strong precipitation and wind velocity negatively affect lamb survival, while temperature and ANPP are positively correlated. The impact of extreme weather events on ANP and sheep production (SP) was in most of the cases significantly negative, with the exception of maximum temperature that correlated with an increase of ANPP, and droughts that showed a non-significant negative trend in ANPP. The examination of these relationships is urgent under the current scenario of climate change with the acceleration of the environmental trends here detected.
One of the most polluted areas in Chile is the Ventanas Industrial Area (VIA; 32.74°S / 71.48°W), which started in 1958 and today comprises around 16 industries in an area of ca. 4 km2. A lack of ...consistent long-term instrumental records precludes assessing the history of contamination in the area and also limits the evaluation of mitigation actions taken since the late 1980s. Here, we use dendrochemistry as an environmental proxy to analyze environmental changes over several decades at the VIA. We present chemical measurements of tree rings from planted, exotic Cupressus macrocarpa growing near the VIA with 4-year resolution over a period of 52 years (1960–2011). These data provide unprecedented information on regional anthropogenic pollution and are compared with a tree-ring elemental record of 48 years (1964–2011) from the Isla Negra (INE) control site not exposed to VIA emissions. For the 48 years of overlap between both sites, higher concentrations of Zn, V, Co, Cd, Ag, Fe, Cr, and Al were especially registered after the year 2000 at VIA compared to INE for the periods under study. Concentrations of Pb, Cu, As, Fe, Mo, Cr, and Zn increased through time, particularly over the period 1980–1990. Decontamination plans activated in 1992 appear to have had a positive effect on the amount of some elements, but the chemical concentration in the tree rings suggest continued accumulation of pollutants in the environment. Only after several years of implementation of the mitigation measures have some elements tended to decrease in concentration, especially at the end of the evaluated period. Dendrochemistry is a useful tool to provide a long-term perspective of the dynamics of trace metal pollution and represents a powerful approach to monitor air quality variability to extend the instrumental records back in time.
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•Pollution trends in mega industrial area in Chile were studied by dendrochemistry•Most of trace element concentration increase in trees close to the industrial area.•Dendrochemistry can be used to provide historic assessments of industrial impacts.
Trees’ growth responses to climate may depend on tree age and site conditions. In dioecious species, sex adds an extra level of complexity due to differential reproductive effort between the sexes ...and potentially sex-related dimorphic growth. Araucaria araucana is a long-lived dioecious conifer with outstanding morphological and functional adaptations considered an excellent model to explore interactions between radial growth, climate variability and reproductive effort. We assessed the potential dimorphism of growth rates of the sexes, the effects of site, tree age and sex on the individual climatic responses, and the growth-climate-cone production relationships of A. araucana in two environmentally contrasted sites at the Andes of south-central Chile. We quantified tree-ring growth, its dependence on weather variability, and the relationships of cone production with growth and climate. We found site-dependent sexually-dimorphic growth rates, with females growing more in the warmer site while males growing more in the colder site. Resource allocation to growth was dependent on weather conditions prior to the growing season. Clear effects of site conditions, tree sex and age on the responses of individual tree growth to climate were identified. A more resilient response to drought stress occurred in the colder site and female trees’ growth showed tighter limitations by winter snow cover. Warm conditions in spring and summer exerted an age-dependent detrimental effect on growth, which is coherent with earlier xylogenesis resumption in younger trees. Cone production was strongly dependent on antecedent weather conditions up to seven years prior to seed dispersal that induced female cone primordia formation and favoured fertilization of female cones and soil nutrient uptake. The revealed lagged connections between vegetative growth, weather cues and cone production point towards a long-term life strategy for A. araucana.
•N. pumilio growth has declined reaching its lowest level during the last 100years.•N. pumilio growth is negatively correlated with precipitation in late spring.•N. pumilio growth is positively ...correlated with temperature in late spring and early summer.•Tree growth is intermittently associated to the variations of ENSO and AAO.
Global warming is expected to enhance radial tree growth at alpine treeline sites worldwide. We developed a well-replicated tree-ring chronology from Nothofagus pumilio near treeline in a high precipitation climate on Choshuenco Volcano (40°S) in Chile to examine: (a) variation in tree radial growth in relation to interannual climatic variability; and (b) relationships of radial growth to variability in El Niño Southern Oscillation (ENSO) and the Antarctic Oscillation (AAO) at interannual and decadal time scales. A tree-ring chronology based on 99 tree-ring series from 80 N. pumilio trees near treeline showed a high series intercorrelation (0.48) indicating a strong common environmental signal. Radial growth is negatively correlated with precipitation in late spring (November–December). Temperature and tree growth are positively correlated during late spring and early summer (November–January). Interannual variability in both seasonal climate and in tree growth is strongly teleconnected to ENSO and AAO variability. Radial growth of N. pumilio in this humid high-elevation forest does not show a positive trend over the past half century as predicted from global treeline theory and broadscale warming in the Patagonian-Andean region. Instead, tree growth increased sharply from the 1960s to a peak in the early 1980s but subsequently declined for c. 30years to its lowest level in >100years. The shift to higher radial growth after c. 1976 coincides with a shift towards warmer sea surface temperatures in the tropical Pacific which in turn are associated with warmer growing season temperatures. The decline in tree growth since the mid-1990s is coincident with the increasingly positive phase of the AAO and high spring precipitation periods associated with El Niño conditions. The recent shift towards reduced growth of N. pumilio at this humid high-elevation site coincident with rising AAO mirrors the reduced tree growth beginning in the 1960s for trees growing in relatively xeric, lower elevation sites throughout the Patagonian-Andean region. The current study indicates that N. pumilio growth response in humid high-elevation environments to recent broad-scale warming has been non-linear, and that AAO and ENSO are key climatic forcings of tree growth variability.
In the Mediterranean Andes region (MA; 30°–37°S), the main rivers are largely fed by melting snowpack and provide freshwater to around 10 million people on both sides of the Andes Mountains. Water ...resources in the MA are under pressure because of the extensive development of industrial agriculture and mining activities. This pressure is increasing as the region faces one of its worst recorded droughts. Previous studies have pointed to El Niño–Southern Oscillation (ENSO) as the main climatic force impacting the MA. However, the role of decadal and multidecadal climate variability, their spatial patterns, and the recurrence of long-term droughts remains poorly studied. In an attempt to better understand these factors, spatial and temporal patterns of hydroclimatic variability are analyzed using an extensive database of streamflow, precipitation, and snowpack covering the period between 1910 and 2011. These analyses are based on the combination of correlation, principal components, and kernel estimation techniques. Despite a general common pattern across the MA, the results presented here identify two hydroclimatic subregions, located north and south of 348S. While the interannual variability associated with ENSO is slightly stronger north of 348S, the variability associated with the Pacific decadal oscillation (PDO) and/or the interdecadal Pacific oscillation (IPO) index shows similar patterns in both regions. However, variations produced by the IPO forcing seem to be greater in the southern subregion since 1975. The estimations presented here on drought recurrence reveal a generalized increase in dry extremes since the 1950s. These findings suggest that the northern MA is more vulnerable to changes in hydrology and climate than the southern MA.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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