Wildfire activity in rainforests in western Patagonia linked to the Southern Annular Mode

2012 ◽  
Vol 21 (2) ◽  
pp. 114 ◽  
Author(s):  
Andrés Holz ◽  
Thomas T. Veblen
Keyword(s):  
Fire History ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Regional Climate ◽  
Southern Annular Mode ◽  
Strong Increase ◽  
Annular Mode ◽  
Decadal Scale ◽  
In Fire

Increased wildfire activity in relation to future climate warming is likely for temperate rainforest biomes where fire depends on anomalously dry fuel conditions. Tree-ring fire history records were developed from fires scars in western Patagonia, and synchrony in fire activity was examined to determine the role of regional climate variability in promoting fires. Interannual variability in the multicentury fire history records was related to El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and the Southern Annular Mode (SAM). Interannual fire synchrony and decadal-scale trends in wildfires document a strong influence of broad-scale climatic variability on wildfires in western Patagonia. SAM is above average during years of regional drought that coincide with widespread fires. Analyses of contingent interactions of ENSO, PDO and SAM revealed that fire frequencies were greater than expected only when SAM was in its positive phase, regardless of the phase of ENSO and PDO. The fire-enhancing influence of SAM was greatest when PDO was also positive, which indicates Pacific-wide warmer conditions. There is a strong increase in wildfire activity coincident with warming and drying trends during the 20th century and with variability in SAM, which is predicted to continue to be in this fire-conducive phase for the 21st century.

scholarly journals Fire history in western Patagonia from paired tree-ring fire-scar and charcoal records

2012 ◽  
Vol 8 (2) ◽  
pp. 451-466 ◽  
Author(s):  
A. Holz ◽  
S. Haberle ◽  
T. T. Veblen ◽  
R. De Pol-Holz ◽  
J. Southon
Keyword(s):  
South America ◽  
Tree Ring ◽  
Large Scale ◽  
Fire History ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Regional Climate ◽  
Southern South America ◽  
Fire Scar ◽  
Fire Activity

Abstract. Fire history reconstructions are typically based on tree ages and tree-ring fire scars or on charcoal in sedimentary records from lakes or bogs, but rarely on both. In this study of fire history in western Patagonia (47–48° S) in southern South America (SSA) we compared three sedimentary charcoal records collected in bogs with tree-ring fire-scar data collected at 13 nearby sample sites. We examined the temporal and spatial correspondence between the two fire proxies and also compared them to published charcoal records from distant sites in SSA, and with published proxy reconstructions of regional climate variability and large-scale climate modes. Two of our three charcoal records record fire activity for the last 4 ka yr and one for the last 11 ka yr. For the last ca. 400 yr, charcoal accumulation peaks tend to coincide with high fire activity in the tree-ring fire scar records, but the charcoal records failed to detect some of the fire activity recorded by tree rings. Potentially, this discrepancy reflects low-severity fires that burn in herbaceous and other fine fuels without depositing charcoal in the sedimentary record. Periods of high fire activity tended to be synchronous across sample areas, across proxy types, and with proxy records of regional climatic variability as well as major climate drivers. Fire activity throughout the Holocene in western Patagonia has responded to regional climate variation affecting a broad region of southern South America that is teleconnected to both tropical- and high-latitude climate drivers-El Niño-Southern Oscillation and the Southern Annular Mode. An early Holocene peak in fire activity pre-dates any known human presence in our study area, and consequently implicates lightning as the ignition source. In contrast, the increased fire activity during the 20th century, which was concomitantly recorded by charcoal from all the sampled bogs and at all fire-scar sample sites, is attributed to human-set fires and is outside the range of variability characteristic of these ecosystems over many centuries and probably millennia.

scholarly journals Fire history in western Patagonia from paired tree-ring fire-scar and charcoal records

2011 ◽  
Vol 7 (5) ◽  
pp. 3203-3238 ◽  
Author(s):  
A. Holz ◽  
S. Haberle ◽  
T. T. Veblen ◽  
R. De Pol-Holz ◽  
J. Southon
Keyword(s):  
South America ◽  
Tree Ring ◽  
Large Scale ◽  
Fire History ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Regional Climate ◽  
Southern South America ◽  
Fire Scar ◽  
Fire Activity

Abstract. Fire history reconstructions are typically based on tree ages and tree-ring fire scars or on charcoal in sedimentary records from lakes or bogs, but rarely on both. In this study of fire history in western Patagonia (47–48° S) in southern South America (SSA) we compared three sedimentary charcoal records collected in bogs with tree-ring fire-scar data collected at 13 nearby sample sites. We examined the temporal and spatial correspondence between the two fire proxies and also compared them to published charcoal records from distant sites in SSA, and with published proxy reconstructions of regional climate variability and large-scale climate modes. Two of our three charcoal records show fire activity for the last 4ka yrs and one for the last 11 ka yr. For the last ca. 400 yr, charcoal accumulation peaks tend to coincide with high fire activity in the tree-ring fire scar records, but the charcoal records failed to detect some of the fire activity recorded by tree rings. Potentially, this discrepancy reflects low-severity fires that burn in herbaceous and other fine fuels without depositing charcoal in the sedimentary record. Periods of high fire activity tended to be synchronous across sample areas, across proxy types, and with proxy records of regional climatic variability as well as major climate drivers. Fire activity throughout the Holocene in western Patagonia has responded to regional climate variation affecting a broad region of southern South America that is teleconnected to both tropical- and high-latitude climate drivers – El Nino-Southern Oscillation and the Southern Annular Mode. An early Holocene peak in fire activity pre-dates any known human presence in our study area, and consequently implicates lightning as the ignition source. In contrast, the increased fire activity during the 20th century, which was concomitantly recorded by charcoal from all the sampled bogs and at all fire-scar sample sites, is attributed to human-set fires and is outside the range of variability characteristic of these ecosystems over many centuries and probably millennia.

Differential Credibility of Climate Modes in CMIP6

2021 ◽  
pp. 1
Author(s):  
Jacob Coburn ◽  
S.C. Pryor
Keyword(s):  
Southern Oscillation ◽  
Probability Distributions ◽  
Critical Role ◽  
Regional Scale ◽  
Southern Annular Mode ◽  
Climate Projections ◽  
Annular Mode ◽  
Climate Modes ◽  
First Order ◽  
Skill Scores

AbstractThis work quantitatively evaluates the fidelity with which the Northern Annular Mode (NAM), Southern Annular Mode (SAM), Pacific-North American pattern (PNA), El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) and the first-order mode interactions are represented in Earth System Model (ESM) output from the CMIP6 archive. Several skill metrics are used as part of a differential credibility assessment (DCA) of both spatial and temporal characteristics of the modes across ESMs, ESM families and specific ESM realizations relative to ERA5. The spatial patterns and probability distributions are generally well represented but skill scores that measure the degree to which the frequencies of maximum variance are captured are consistently lower for most ESMs and climate modes. Substantial variability in skill scores manifests across realizations from individual ESMs for the PNA and oceanic modes. Further, the ESMs consistently overestimate the strength of the NAM-PNA first-order interaction and underestimate the NAM-AMO connection. These results suggest that the choice of ESM and ESM realizations will continue to play a critical role in determining climate projections at the global and regional scale at least in the near-term.

Regional climate impacts of the Southern Annular Mode

2006 ◽  
Vol 33 (23) ◽  
Author(s):  
N. P. Gillett ◽  
T. D. Kell ◽  
P. D. Jones
Keyword(s):  
Regional Climate ◽  
Southern Annular Mode ◽  
Climate Impacts ◽  
Annular Mode

scholarly journals Teleconnections and relationship between the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) in reconstructions and models over the past millennium

2020 ◽  
Vol 16 (2) ◽  
pp. 743-756 ◽  
Author(s):  
Christoph Dätwyler ◽  
Martin Grosjean ◽  
Nathan J. Steiger ◽  
Raphael Neukom
Keyword(s):  
Climate Model ◽  
El Nino ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
Last Millennium ◽  
Annular Mode ◽  
Model Simulations ◽  
The Past ◽  
Climate Model Simulations ◽  
Past Millennium

Abstract. The climate of the Southern Hemisphere (SH) is strongly influenced by variations in the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Because of the limited length of instrumental records in most parts of the SH, very little is known about the relationship between these two key modes of variability over time. Using proxy-based reconstructions and last-millennium climate model simulations, we find that ENSO and SAM indices are mostly negatively correlated over the past millennium. Pseudo-proxy experiments indicate that currently available proxy records are able to reliably capture ENSO–SAM relationships back to at least 1600 CE. Palaeoclimate reconstructions show mostly negative correlations back to about 1400 CE. An ensemble of last-millennium climate model simulations confirms this negative correlation, showing a stable correlation of approximately −0.3. Despite this generally negative relationship we do find intermittent periods of positive ENSO–SAM correlations in individual model simulations and in the palaeoclimate reconstructions. We do not find evidence that these relationship fluctuations are caused by exogenous forcing nor by a consistent climate pattern. However, we do find evidence that strong negative correlations are associated with strong positive (negative) anomalies in the Interdecadal Pacific Oscillation and the Amundsen Sea Low during periods when SAM and ENSO indices are of opposite (equal) sign.

Large-Scale Atmospheric Drivers of Snowfall on Thwaites Glacier

2020 ◽  
Author(s):  
Michelle Maclennan ◽  
Jan Lenaerts
Keyword(s):  
Temporal Variability ◽  
Large Scale ◽  
Climate Model ◽  
Southern Oscillation ◽  
Regional Climate ◽  
Southern Annular Mode ◽  
Spatial And Temporal Variability ◽  
Atmospheric Conditions ◽  
Amundsen Sea ◽  
Weather Patterns

<p>High snowfall events on Thwaites Glacier are a key influencer of its ice mass change. In this study, we diagnose the mechanisms for orographic precipitation on Thwaites Glacier by analyzing the atmospheric conditions that lead to high snowfall events. A high-resolution regional climate model, RACMO2, is used in conjunction with MERRA-2 and ERA5 reanalysis to map snowfall and associated atmospheric conditions over the Amundsen Sea Embayment. We examine these conditions during high snowfall events over Thwaites Glacier to characterize the drivers of the precipitation and their spatial and temporal variability. Then we examine the seasonal differences in the associated weather patterns and their correlations with El Nino Southern Oscillation and the Southern Annular Mode. Understanding the large-scale atmospheric drivers of snowfall events allows us to recognize how these atmospheric drivers and consequent snowfall climatology will change in the future, which will ultimately improve predictions of accumulation on Thwaites Glacier.</p>

scholarly journals Decadal Variability of the ENSO Teleconnection to the High-Latitude South Pacific Governed by Coupling with the Southern Annular Mode*

2006 ◽  
Vol 19 (6) ◽  
pp. 979-997 ◽  
Author(s):  
Ryan L. Fogt ◽  
David H. Bromwich
Keyword(s):  
High Latitude ◽  
Decadal Variability ◽  
Southern Oscillation ◽  
Phase Relationship ◽  
South Pacific ◽  
Southern Annular Mode ◽  
Height Anomaly ◽  
Austral Spring ◽  
Annular Mode ◽  
The Pacific

Abstract Decadal variability of the El Niño–Southern Oscillation (ENSO) teleconnection to the high-latitude South Pacific is examined by correlating the European Centre for Medium-Range Weather Forecasts (ECMWF) 40-yr Re-Analysis (ERA-40) and observations with the Southern Oscillation index (SOI) over the last two decades. There is a distinct annual contrast between the 1980s and the 1990s, with the strong teleconnection in the 1990s being explained by an enhanced response during austral spring. Geopotential height anomaly composites constructed during the peak ENSO seasons also demonstrate the decadal variability. Empirical orthogonal function (EOF) analysis reveals that the 1980s September–November (SON) teleconnection is weak due to the interference between the Pacific–South American (PSA) pattern associated with ENSO and the Southern Annular Mode (SAM). An in-phase relationship between these two modes during SON in the 1990s amplifies the height and pressure anomalies in the South Pacific, producing the strong teleconnections seen in the correlation and composite analyses. The in-phase relationship between the tropical and high-latitude forcing also exists in December–February (DJF) during the 1980s and 1990s. These results suggest that natural climate variability plays an important role in the variability of SAM, in agreement with a growing body of literature. Additionally, the significantly positive correlation between ENSO and SAM only during times of strong teleconnection suggests that both the Tropics and the high latitudes need to work together in order for ENSO to strongly influence Antarctic climate.

scholarly journals Rainfall Changes over Southwestern Australia and Their Relationship to the Southern Annular Mode and ENSO

2014 ◽  
Vol 27 (15) ◽  
pp. 5801-5814 ◽  
Author(s):  
Bhupendra A. Raut ◽  
Christian Jakob ◽  
Michael J. Reeder
Keyword(s):  
Southern Oscillation ◽  
Summer Rainfall ◽  
Southern Annular Mode ◽  
Winter Rainfall ◽  
Sea Level Pressure ◽  
Annular Mode ◽  
Southwestern Australia ◽  
Synoptic Conditions ◽  
The Mean ◽  
Rainfall Patterns

Abstract Since the 1970s, winter rainfall over coastal southwestern Australia (SWA) has decreased by 10%–20%, while summer rainfall has been increased by 40%–50% in the semiarid inland area. In this paper, a K-means algorithm is used to cluster rainfall patterns directly as opposed to the more conventional approach of clustering synoptic conditions (usually the mean sea level pressure) and inferring the associated rainfall. It is shown that the reduction in the coastal rainfall during winter is mainly due to fewer westerly fronts in June and July. The reduction in the frequency of strong fronts in June is responsible for half of the decreased rainfall in June–August (JJA), whereas the reduction in the frequency of weaker fronts in June and July accounts for a third of the total decrease. The increase in rainfall inland in December–February (DJF) is due to an increased frequency of easterly troughs in December and February. These rainfall patterns are linked to the southern annular mode (SAM) index and Southern Oscillation index (SOI). The reduction in coastal rainfall and the increase in rainfall inland are both related to the predominantly positive phase of SAM, especially when the phase of ENSO is neutral.

scholarly journals Fire history in the Araucaria araucana forests of Argentina: human and climate influences

2013 ◽  
Vol 22 (2) ◽  
pp. 194 ◽  
Author(s):  
I. A. Mundo ◽  
T. Kitzberger ◽  
F. A. Roig Juñent ◽  
R. Villalba ◽  
M. D. Barrera
Keyword(s):  
Human Activities ◽  
Fire History ◽  
Southern Oscillation ◽  
Fire Regimes ◽  
Southern Annular Mode ◽  
Temporal Variations ◽  
La Niña ◽  
La Nina ◽  
Araucaria Araucana ◽  
Climate Influences

Little is known about drivers and trends of historic fire regimes in the Araucaria araucana forests of south-western Argentina. Fire history in these forests was reconstructed by the analysis of 246 fire-scarred partial cross-sections from this fire-resistant tree collected at 10 sites in Neuquén, northern Patagonia. Fire chronologies showed an increase in fire occurrence during the nineteenth century and a sharp decrease since the early twentieth century. The creation of Lanín National Park in 1937, the change in human activities, and the active suppression of wildfires led to a significant increase in mean fire intervals since 1930. In addition to these multidecadal to centennial scale drives of fire frequency, interannual variability in wildfire activity was associated with El Niño–Southern Oscillation. Years of widespread fire are related to negative departures of both Niño 3.4 and Pacific Decadal Oscillation indexes (i.e. La Niña conditions), as well as coincident phases of positive Southern Annular Mode and La Niña events. Temporal variations in the Araucaria fire history in Argentina clearly show the combined effect of human and climate influences on fire regimes. A comparison with previous fire history studies in the Araucaria forests of Chile reveals substantial differences related to differences in human activities on both sides of the Andes and the earlier implementation of protected areas in Argentina.

Sign in / Sign up

Export Citation Format

Share Document