Southern Annular Mode response to volcanic eruptions: implications for ice-core proxies

Decadal Climate Oscillations, Synoptic Variability, and Ice Core Climate Proxy Records in the Ross Sea Region, Antarctica

10.26686/wgtn.17000299 ◽

2021 ◽

Author(s):

◽

Bradley Ross Markle

Keyword(s):

Ross Sea ◽

Ice Core ◽

Southern Annular Mode ◽

Future Climate Change ◽

Climate Oscillations ◽

Annular Mode ◽

Synoptic Variability ◽

Proxy Records ◽

Synoptic Conditions ◽

Decadal Climate

<p>This thesis investigates synoptic variability in the Ross Sea region, Antarctica and develops geochemical proxies of this variability from an ice core record in Southern Victoria Land. Particular focus is given to the influence of decadal climate oscillations on synoptic conditions and potential records of these oscillations in ice core proxy records as long-‐term records of these oscillations are important for understanding future climate change. I present an investigation of the joint influence of the El Niño Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) on variability in the Amundsen Sea Low (ASL), a dominant climatological feature that strongly influences the weather in the Ross Sea region. It is shown that the positive phase of each oscillation is associated with significant strengthening of the ASL, while negative phases are associated with a weakening. Through regression analysis I show that a simple linear combination of indices representing these oscillations can explain more than 40% of the geopotential height variance in the AS region at a seasonal scale and over 70% of the variance at an annual scale. These results are consistent with the known mechanisms of ENSO and SAM interaction in the region and show that while SAM is dominant hemispherically, ENSO is only influential in the Pacific Sector. Finally it is demonstrated that a simple model of linear reinforcement and interference between the oscillations describes their influence on the variability in the ASL better than models incorporating more complex interactions. Atmospheric back-‐trajectory modeling and cluster analysis are used to investigate synoptic variability at the Gawn Ice Piedmont (GIP) ice core site in the Ross Sea Region, Antarctica. I identify two dominant air-‐mass trajectory clusters: oceanic – cyclonic and continental trajectories. My analysis shows that oceanic – cyclonic trajectories peak during April (southern hemisphere winter), while continental trajectories reach their maximum during December (summer). A causal association is demonstrated between ENSO and the frequency of oceanic – cyclonic trajectories originating from the Ross Sea region. In contrast, it is shown that the Southern Annular Mode has little influence on the frequency of cyclonic clusters. I then develop proxy records for the synoptic variability using a shallow firn core from the GIP site containing 8 years of geochemical record. Continental trajectories correlate with concentrations of nitrate (NO3), which is sourced from stratospheric air-‐masses descending over the Antarctic interior. Oceanic – cyclonic trajectory clusters strongly correlate with deuterium excess at seasonal and inter-‐annual scales, a proxy sensitive to changes in relative humidity and sea surface temperature (SST) in the in the Ross and Amundsen Seas. Decadal variability in the frequency of oceanic – cyclonic trajectories is discussed with respect to ENSO, SAM, and changes in SST and sea ice extent.</p>

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High-latitude Southern Hemisphere fire history during the mid- to late Holocene (6000–750 BP)

Climate of the Past ◽

10.5194/cp-14-871-2018 ◽

2018 ◽

Vol 14 (6) ◽

pp. 871-886 ◽

Cited By ~ 9

Author(s):

Dario Battistel ◽

Natalie M. Kehrwald ◽

Piero Zennaro ◽

Giuseppe Pellegrino ◽

Elena Barbaro ◽

...

Keyword(s):

Southern Hemisphere ◽

Biomass Burning ◽

Late Holocene ◽

Fire History ◽

Ice Core ◽

Southern Annular Mode ◽

Major Influence ◽

Cool Period ◽

Annular Mode ◽

Southern Patagonia

Abstract. We determined the specific biomass burning biomarker levoglucosan in an ice core from the TALos Dome Ice CorE drilling project (TALDICE) during the mid- to late Holocene (6000–750 BP). The levoglucosan record is characterized by a long-term increase with higher rates starting at ∼ 4000 BP and peaks between 2500 and 1500 BP. The anomalous increase in levoglucosan centered at ∼ 2000 BP is consistent with other Antarctic biomass burning records. Multiple atmospheric phenomena affect the coastal Antarctic Talos Dome drilling site, where the Southern Annular Mode (SAM) is the most prominent as the Southern Annular Mode Index (SAMA) correlates with stable isotopes in precipitation throughout the most recent 1000 years of the ice core. If this connection remains throughout the mid- to late Holocene, then our results demonstrate that changes in biomass burning, rather than changes in atmospheric transport, are the major influence on the TALDICE levoglucosan record. Comparisons with charcoal syntheses help evaluate fire sources, showing a greater contribution from southern South American fires than from Australian biomass burning. The levoglucosan peak centered at ∼ 2000 BP occurs during a cool period throughout the Southern Hemisphere, yet during a time of increased fire activity in both northern and southern Patagonia. This peak in biomass burning is influenced by increased vegetation in southern South America from a preceding humid period, in which the vegetation desiccated during the following cool, dry period. The Talos Dome ice core record from 6000 to ∼ 750 BP currently does not provide clear evidence that the fire record may be strongly affected by anthropogenic activities during the mid- to late Holocene, although we cannot exclude at least a partial influence.

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Dynamical and hydrological changes in climate simulations of the last millennium

Climate of the Past ◽

10.5194/cp-16-1285-2020 ◽

2020 ◽

Vol 16 (4) ◽

pp. 1285-1307

Author(s):

Pedro José Roldán-Gómez ◽

Jesús Fidel González-Rouco ◽

Camilo Melo-Aguilar ◽

Jason E. Smerdon

Keyword(s):

Principal Component ◽

Volcanic Eruptions ◽

Southern Annular Mode ◽

Ice Age ◽

Last Millennium ◽

External Forcing ◽

Annular Mode ◽

Hydrological Changes ◽

Intercomparison Project ◽

Convergence Zones

Abstract. Simulations of climate of the last millennium (LM) show that external forcing had a major contribution to the evolution of temperatures; warmer and colder periods like the Medieval Climate Anomaly (MCA; ca. 950–1250 CE) and the Little Ice Age (LIA; ca. 1450–1850 CE) were critically influenced by changes in solar and volcanic activity. Even if this influence is mainly observed in terms of temperatures, evidence from simulations and reconstructions shows that other variables related to atmospheric dynamics and hydroclimate were also influenced by external forcing over some regions. In this work, simulations from the Coupled Model Intercomparison Project Phase 5 and Paleoclimate Modelling Intercomparison Project Phase 3 (CMIP5/PMIP3) are analyzed to explore the influence of external forcings on the dynamical and hydrological changes during the LM at different spatial and temporal scales. Principal component (PC) analysis is used to obtain the modes of variability governing the global evolution of climate and to assess their correlation with the total external forcing at multidecadal to multicentennial timescales. For shorter timescales, a composite analysis is used to address the response to specific events of external forcing like volcanic eruptions. The results show coordinated long-term changes in global circulation patterns, which suggest expansions and contractions of the Hadley cells and latitudinal displacements of westerlies in response to external forcing. For hydroclimate, spatial patterns of drier and wetter conditions in areas influenced by the North Atlantic Oscillation (NAO), Northern Annular Mode (NAM), and Southern Annular Mode (SAM) and alterations in the intensity and distribution of monsoons and convergence zones are consistently found. Similarly, a clear short-term response is found in the years following volcanic eruptions. Although external forcing has a greater influence on temperatures, the results suggest that dynamical and hydrological variations over the LM exhibit a direct response to external forcing at both long and short timescales that is highly dependent on the particular simulation and model.

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Decadal Climate Oscillations, Synoptic Variability, and Ice Core Climate Proxy Records in the Ross Sea Region, Antarctica

10.26686/wgtn.17000299.v1 ◽

2021 ◽

Author(s):

◽

Bradley Ross Markle

Keyword(s):

Ross Sea ◽

Ice Core ◽

Southern Annular Mode ◽

Future Climate Change ◽

Climate Oscillations ◽

Annular Mode ◽

Synoptic Variability ◽

Proxy Records ◽

Synoptic Conditions ◽

Decadal Climate

<p>This thesis investigates synoptic variability in the Ross Sea region, Antarctica and develops geochemical proxies of this variability from an ice core record in Southern Victoria Land. Particular focus is given to the influence of decadal climate oscillations on synoptic conditions and potential records of these oscillations in ice core proxy records as long-‐term records of these oscillations are important for understanding future climate change. I present an investigation of the joint influence of the El Niño Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) on variability in the Amundsen Sea Low (ASL), a dominant climatological feature that strongly influences the weather in the Ross Sea region. It is shown that the positive phase of each oscillation is associated with significant strengthening of the ASL, while negative phases are associated with a weakening. Through regression analysis I show that a simple linear combination of indices representing these oscillations can explain more than 40% of the geopotential height variance in the AS region at a seasonal scale and over 70% of the variance at an annual scale. These results are consistent with the known mechanisms of ENSO and SAM interaction in the region and show that while SAM is dominant hemispherically, ENSO is only influential in the Pacific Sector. Finally it is demonstrated that a simple model of linear reinforcement and interference between the oscillations describes their influence on the variability in the ASL better than models incorporating more complex interactions. Atmospheric back-‐trajectory modeling and cluster analysis are used to investigate synoptic variability at the Gawn Ice Piedmont (GIP) ice core site in the Ross Sea Region, Antarctica. I identify two dominant air-‐mass trajectory clusters: oceanic – cyclonic and continental trajectories. My analysis shows that oceanic – cyclonic trajectories peak during April (southern hemisphere winter), while continental trajectories reach their maximum during December (summer). A causal association is demonstrated between ENSO and the frequency of oceanic – cyclonic trajectories originating from the Ross Sea region. In contrast, it is shown that the Southern Annular Mode has little influence on the frequency of cyclonic clusters. I then develop proxy records for the synoptic variability using a shallow firn core from the GIP site containing 8 years of geochemical record. Continental trajectories correlate with concentrations of nitrate (NO3), which is sourced from stratospheric air-‐masses descending over the Antarctic interior. Oceanic – cyclonic trajectory clusters strongly correlate with deuterium excess at seasonal and inter-‐annual scales, a proxy sensitive to changes in relative humidity and sea surface temperature (SST) in the in the Ross and Amundsen Seas. Decadal variability in the frequency of oceanic – cyclonic trajectories is discussed with respect to ENSO, SAM, and changes in SST and sea ice extent.</p>

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Dynamical and hydrological changes in climate simulations of the last millennium

10.5194/cp-2020-8 ◽

2020 ◽

Author(s):

Pedro José Roldán-Gómez ◽

Jesús Fidel González-Rouco ◽

Camilo Melo-Aguilar ◽

Jason E. Smerdon

Keyword(s):

Principal Component ◽

Volcanic Eruptions ◽

Southern Annular Mode ◽

Ice Age ◽

Last Millennium ◽

External Forcing ◽

Annular Mode ◽

Hydrological Changes ◽

Intercomparison Project ◽

Convergence Zones

Abstract. Simulations of last millennium (LM) climate show that external forcing had a major contribution to the evolution of temperatures; warmer and colder periods like the Medieval Climate Anomaly (MCA; ca. 950–1250 CE) and the Little Ice Age (LIA; ca. 1450–1850 CE) were critically influenced by changes in solar and volcanic activity. Even if this influence is mainly observed in terms of temperatures, evidence from simulations and reconstructions show that other variables related to atmospheric dynamics and hydroclimate also were influenced by external forcing over some regions. In this work, simulations from the Coupled Model Intercomparison Project Phase 5/Paleoclimate Modelling Intercomparison Project Phase 3 (CMIP5/PMIP3) are analyzed to explore the influence of external forcings on the dynamical and hydrological changes during the LM at different spatial and temporal scales. Principal Component (PC) analysis is used to obtain the modes of variability governing the global evolution of climate and to assess their correlation with the total external forcing at multidecadal to multicentennial timescales. For shorter timescales, a composite analysis is used to address the response to specific events of external forcing like volcanic eruptions. The results show coordinated long-term changes in global circulation patterns, which suggest expansions and contractions of the Hadley Cells and latitudinal displacements of Westerlies in response to external forcing. For hydroclimate, spatial patterns of drier and wetter conditions in areas influenced by the North Atlantic Oscillation (NAO), Northern Annular Mode (NAM) and Southern Annular Mode (SAM) and alterations in the intensity and distribution of monsoons and convergence zones are consistently found. Similarly, a clear short-term response is found in the years following volcanic eruptions. Although external forcing has a larger influence on temperatures, the results suggest that dynamical and hydrological variations over the LM exhibit a direct response to external forcing both at long and short timescales that is highly dependent on the particular simulation and model.

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Assessment of zonally symmetric and asymmetric components of the Southern Annular Mode using a novel approach

Climate Dynamics ◽

10.1007/s00382-021-05896-5 ◽

2021 ◽

Author(s):

Elio Campitelli ◽

Leandro B. Díaz ◽

Carolina Vera

Keyword(s):

Southern Annular Mode ◽

Annular Mode ◽

Novel Approach

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The Impact of ENSO on Wave Breaking and Southern Annular Mode Events

Journal of the Atmospheric Sciences ◽

10.1175/2010jas3311.1 ◽

2010 ◽

Vol 67 (9) ◽

pp. 2854-2870 ◽

Cited By ~ 47

Author(s):

Tingting Gong ◽

Steven B. Feldstein ◽

Dehai Luo

Keyword(s):

El Niño ◽

Wave Breaking ◽

El Nino ◽

Southern Annular Mode ◽

La Niña ◽

Background Flow ◽

Austral Spring ◽

Annular Mode ◽

La Nina ◽

The Impact

Abstract This study examines the relationship between intraseasonal southern annular mode (SAM) events and the El Niño–Southern Oscillation (ENSO) using daily 40-yr ECMWF Re-Analysis (ERA-40) data. The data coverage spans the years 1979–2002, for the austral spring and summer seasons. The focus of this study is on the question of why positive SAM events dominate during La Niña and negative SAM events during El Niño. A composite analysis is performed on the zonal-mean zonal wind, Eliassen–Palm fluxes, and two diagnostic variables: the meridional potential vorticity gradient, a zonal-mean quantity that is used to estimate the likelihood of wave breaking, and the wave breaking index (WBI), which is used to evaluate the strength of the wave breaking. The results of this investigation suggest that the background zonal-mean flow associated with La Niña (El Niño) is preconditioned for strong (weak) anticyclonic wave breaking on the equatorward side of the eddy-driven jet, the type of wave breaking that is found to drive positive (negative) SAM events. A probability density function analysis of the WBI, for both La Niña and El Niño, indicates that strong anticyclonic wave breaking takes place much more frequently during La Niña and weak anticyclonic wave breaking during El Niño. It is suggested that these wave breaking characteristics, and their dependency on the background flow, can explain the strong preference for SAM events of one phase during ENSO. The analysis also shows that austral spring SAM events that coincide with ENSO are preceded by strong stratospheric SAM anomalies and then are followed by a prolonged period of wave breaking that lasts for approximately 30 days. These findings suggest that the ENSO background flow also plays a role in the excitation of stratospheric SAM anomalies and that the presence of these stratospheric SAM anomalies in turn excites and then maintains the tropospheric SAM anomalies via a positive eddy feedback.

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Chemical Composition of Ice Containing Tephra Layers in the Byrd Station Ice Core, Antarctica

Quaternary Research ◽

10.1016/0033-5894(88)90007-5 ◽

1988 ◽

Vol 30 (3) ◽

pp. 315-330 ◽

Cited By ~ 9

Author(s):

Julie M. Palais ◽

Philip R. Kyle

Keyword(s):

Chemical Composition ◽

Silicate Glass ◽

Residence Time ◽

Volcanic Ash ◽

Global Climate ◽

Ice Core ◽

Volcanic Eruptions ◽

Tephra Layers ◽

The Antarctic ◽

Hydrolysis Of

The chemical composition of ice containing tephra (volcanic ash) layers in 22 sections of the Byrd Station ice core was examined to determine if the volcanic eruptions affected the chemical composition of the atmosphere and precipitation in the vicinity of Byrd Station. The liquid conductivity, acidity, sulfate, nitrate, aluminum, and sodium concentrations of ice samples deposited before, during, and after the deposition of the tephra layers were analyzed. Ice samples that contain tephra layers have, on average, about two times more sulfate and three to four times more aluminum than nonvolcanic ice samples. The acidity of ice samples associated with tephra layers is lowered by hydrolysis of silicate glass and minerals. Average nitrate, sodium, and conductivity are the same in all samples. Because much of the sulfur and chlorine originally associated with these eruptions may have been scavenged by ash particles, the atmospheric residence time of these volatiles would have been minimized. Therefore the eruptions probably had only a small effect on the composition of the Antarctic atmosphere and a negligible effect on local or global climate.

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