Influence of boundary conditions on the Southern Hemisphere atmospheric circulation during the last glacial maximum

Justino, Flávio; Souza, Ênio Pereira de; Amorim, Mariana Cristina Tavares da Silva Souza; Dias, Pedro; Lemos, Carlos Fernando

doi:10.1590/s0102-77862008000400008

Cited by 4 publications

(6 citation statements)

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“…The pioneer works by Walker and Bilss [1], Bjerknes [2], and Wyrtki [3] are the starting point to the understanding of the El Niño-Southern Oscillation (ENSO), the air-sea interaction, and the decadal climate variability. Recently, studies have analyzed the impacts caused by fluctuations of wind stress on oceanic and atmospheric circulations [4][5][6][7][8][9][10]. This recent motivation is directly related to climate projections for the coming decades.…”

Section: Introductionmentioning

confidence: 99%

Impacts of Wind Stress Changes on the Global Heat Transport, Baroclinic Instability, and the Thermohaline Circulation

Machado

Justino

Pezzi

2016

Advances in Meteorology

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The wind stress is a measure of momentum transfer due to the relative motion between the atmosphere and the ocean. This study aims to investigate the anomalous pattern of atmospheric and oceanic circulations due to 50% increase in the wind stress over the equatorial region and the Southern Ocean. In this paper we use a coupled climate model of intermediate complexity (SPEEDO). The results show that the intensification of equatorial wind stress causes a decrease in sea surface temperature in the tropical region due to increased upwelling and evaporative cooling. On the other hand, the intensification of wind stress over the Southern Ocean induces a regional increase in the air and sea surface temperatures which in turn leads to a reduction in Antarctic sea ice thickness. This occurs in association with changes in the global thermohaline circulation strengthening the rate of Antarctic Bottom Water formation and a weakening of the North Atlantic Deep Water. Moreover, changes in the Southern Hemisphere thermal gradient lead to modified atmospheric and oceanic heat transports reducing the storm tracks and baroclinic activity.

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Section: Introductionmentioning

confidence: 99%

Impacts of Wind Stress Changes on the Global Heat Transport, Baroclinic Instability, and the Thermohaline Circulation

Machado

Justino

Pezzi

2016

Advances in Meteorology

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“…Results found for the ERA‐Interim and CFSR reanalysis for both climatology and anomaly for periods with ENSO displayed few differences for BI and kinetic energy, except for the tendency of the CFSR to present a stronger signal (an overestimation as compared to the ERA‐Interim). However, for the calculation of the meridional heat transport at 500 hPa, the CFSR reanalysis did not perform satisfactorily, since it showed extremely weak transport in relation to the ERA‐Interim and previous studies (Justino, 2004; Machado et al ., 2012).…”

Section: Discussionmentioning

confidence: 86%

“…In this context, the higher the kinetic energy value, the more intense are the high and low pressure systems that are typical of middle latitudes. Thus, the CFSR presents kinetic energy maxima higher than the ERA‐Interim, since due to its increased resolution larger amplitudes are found for its pressure systems (Justino, 2004).…”

Section: Resultsmentioning

confidence: 99%

“…Thus, u ′, v ′ e T ′ represent, in the equation, the deviations from the mean time series (bar) of the daily data after applying the filter and n represents the days in the time series, that is,

\overset{v' T'}{true} = \frac{1}{n} \sum_{1}^{n} ((), v^{'} - \overset{v}{true}) ((), T^{'} - \overset{T}{true}) and \overset{(v'^{bold2} + u'^{bold2})}{true} = \frac{1}{n} \sum_{1}^{n} ((), v^{'} - \overset{v}{true}) + ((), u' - \overset{u}{true})

. This methodology has already been applied by other authors (Justino, 2004; Machado et al ., 2012; Machado et al ., 2016; Freitas et al ., 2019; Yang et al ., 2018).…”

Section: Methodsmentioning

confidence: 99%

“…The preferred regions of formation of extratropical cyclones, known as storm tracks (STs) (Blackmon et al ., 1977), contribute directly to weather and climate, causing changes in near surface air temperature, winds and precipitation amounts. The STs also play a key role in the general circulation of the atmosphere through their strong influence on vertical and horizontal exchanges of heat, water vapour and momentum (Lau, 1988; Justino, 2004). The ST regions are those that present maximum variance of geopotential height in the middle and upper troposphere, resulting from disturbances having a period of approximately 1 week (Hoskins and Valdes, 1990; Justino et al ., 2005).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Influence of El Niño‐Southern Oscillation on baroclinic instability and storm tracks in the Southern Hemisphere

Machado

Justino

Souza

2020

Intl Journal of Climatology

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Earth's weather and climate are strongly influenced by synoptic scale systems such as extratropical cyclones. From this point of view, investigating the mechanisms associated with cyclogenesis, such as baroclinic instability (BI), which are defined by the thermal gradient and wind shear, are extremely important. However, atmospheric teleconnection patterns such as the El Niño-Southern Oscillation (ENSO) phenomenon may affect BI in the preferred region of extratropical cyclones, known as the storm track (ST) region. Therefore, the present study shows the impact of ENSO on BI and STs in the Southern Hemisphere. BI is determined by means of the Eady growth rate method, while the STs are calculated from the kinetic energy and by means of the meridional heat transport. In general, the results show that STs calculated from the BI and the kinetic energy show seasonal variability during ENSO events. This results in Southern Hemisphere extratropical cyclones being more intense with trajectories towards lower (higher) latitudes during El Niño (La Niña) summers. In contrast, little difference is seen in El Niño and La Niña winters. For the calculation of the meridional heat transport at 500 hPa, the Climate Forecast System Reanalysis produced weaker transport relative to ERA-Interim and previous studies.

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Modelling of Quaternary Glacier Extent and Climate in Tasmania, Australia

O'Donnell¹

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<p>The aim of this study was to improve our understanding of Quaternary glaciations in Tasmania, and to assess their climatic significance. During the Quaternary, Tasmania experienced ice cap development in the West Coast Range and Central Plateau, with smaller cirque and valley glaciers developing on surrounding mountains. Geomorphic evidence indicates at least four glacial advances occurred. A 500 m resolution, three-dimensional thermomechanical ice-sheet model was used to reconstruct and simulate these glacier fluctuations. The model, while a simplification of reality, provided a framework in which to understand the genesis of contemporary landforms and former glacial climate conditions in Tasmania. Input specifications of basal topography, temperature and precipitation were required, with the latter two interpolated from present-day datasets. Numerous experiments were carried out, involving systematic alterations to temperature and precipitation, basal sliding and atmospheric temperature lapse-rates. Modelled output was compared to empirical evidence with the aim of optimizing the parameters (temperature, precipitation) from which model mismatch was minimised. An annual temperature reduction of 6' C is required for glaciers to form in Tasmania. When temperatures cool beyond this threshold, an ice mass develops over the Central Highlands, Central Plateau, West Coast Range and other mountains. In all but the most extensive glaciations, the Central Plateau ice field consists of a relatively thin carapace of ice, and the thickest and most dynamic glaciers develop in the deep valleys of the Central Highlands. The model shows that ice readily flows down the west-facing valleys from the Central Highlands to join with West Coast Range glaciers. A temperature reduction between 7 and 9' C, with corresponding regional precipitation changes of between +/-50% and an increase in orographic precipitation is required to simulate the Last Glacial Maximum (LGM) ice cover. Earlier glacial advances require larger coolings of up to 11.25' C depending on the regional precipitation conditions prescribed. Mismatches between geomorphic evidence and modelled reconstructions probably result from model grid size issues and parameters not accommodated by the model such as wind-blown snow redistribution. This means that temperature reductions derived from the model may have been overestimated. Despite these limitations, reconstructed temperatures compare well to some multi-proxy palaeo-temperature records from Tasmania, although the cooling identified was larger than that recorded in nearby ocean sediments.</p>

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Influence of boundary conditions on the Southern Hemisphere atmospheric circulation during the last glacial maximum

Cited by 4 publications

References 30 publications

Impacts of Wind Stress Changes on the Global Heat Transport, Baroclinic Instability, and the Thermohaline Circulation

Impacts of Wind Stress Changes on the Global Heat Transport, Baroclinic Instability, and the Thermohaline Circulation

Influence of El Niño‐Southern Oscillation on baroclinic instability and storm tracks in the Southern Hemisphere

Modelling of Quaternary Glacier Extent and Climate in Tasmania, Australia

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