Consistent past half-century trends in the atmosphere, the sea ice and the ocean at high southern latitudes

Goosse, Hugues; Lefebvre, Wouter; Montety, A. de; Crespin, Elisabeth; Orsi, Alejandro H.

doi:10.1007/s00382-008-0500-9

Cited by 89 publications

(90 citation statements)

References 74 publications

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“…Trends in all of these data are in the direction that would be expected based on studies of the interannual variability in detrended datasets. Results from formal observational data assimilation into a numerical climate model of intermediate complexity are qualitatively in agreement with ours (Goosse et al 2009). We note however that we have not separated the relative roles of multidecadal variability and externally forced climate change, nor fully discriminated the relative roles of tropical SSTs and extratropical SSTs and sea ice in explaining the circulation trends at high Southern latitudes.…”

Section: Summary and Discussionsupporting

confidence: 87%

An assessment and interpretation of the observed warming of West Antarctica in the austral spring

2011

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We synthesize variability and trends in multiple analyses of Antarctic near-surface temperature representing several independent source datasets and spatially complete reconstructions, and place these into the broader context of the behavior of other components of the climate system during the past 30-50 years. Along with an annual-mean trend during the past 50 years of about 0.1°C/decade averaged over Antarctica, there is a distinct seasonality to the trends, with insignificant change (and even some cooling) in austral summer and autumn in East Antarctica, contrasting with warming in austral winter and spring. Apart from the Peninsula, the seasonal warming is largest and most significant in West Antarctica in the austral spring since the late 1970s. Concurrent trends in sea ice are independent evidence of the observed warming over West Antarctic, with the decrease in sea ice area in the Amundsen and Bellingshausen Seas congruent with at least 50% of the inland warming of West Antarctica. Trends in near surface winds and geopotential heights over the high-latitude South Pacific are consistent with a role for atmospheric forcing of the sea ice and air temperature anomalies. Most of the circulation trend projects onto the two Pacific South American (PSA) modes of atmospheric circulation variability, while the Southern Annular Mode lacks a positive trend in spring that would otherwise cause a cooling tendency. The largest circulation trend is associated with the PSA-1 mode, a wave-train extending from the tropics to the high Southern latitudes. The PSA-1 mode is significantly correlated with SSTs in the southwestern tropical and subtropical Pacific. The increased SSTs in this region, together with the observed increase in rainfall, suggest that anomalous deep convection has strengthened or increased the occurrence of the Rossby wave-train associated with PSA-1. This hypothesis is supported by results from two ensembles of SST-forced atmospheric general circulation model simulations. Finally, the implications of the seasonality, timing, and spatial patterns of Antarctic temperature trends with respect to interpreting the relative roles of stratospheric ozone depletion, SSTs and increased atmospheric concentrations of greenhouse gasses are discussed.

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Section: Summary and Discussionsupporting

confidence: 87%

An assessment and interpretation of the observed warming of West Antarctica in the austral spring

2011

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“…There is considerable evidence that the large human-caused decline in stratospheric ozone over this region is the primary driver of recent multidecadal changes in the intensity of the Southern Hemisphere polar vortex (52,53). Such externally forced circulation changes can affect Antarctic sea ice extent (51,54), although the strength (and even the direction) of this effect is still unclear (55). Model simulations with combined forcing by well-mixed greenhouse gases and stratospheric ozone are capable of replicating observed changes in the intensity of the Antarctic polar vortex (52,53), implying that some of the factors driving hemispheric-scale asymmetries in patterns of tropospheric trends may be similar in models and observations.…”

Section: Geographical Patterns Of Temperature Trendsmentioning

confidence: 99%

Identifying human influences on atmospheric temperature

Santer

Painter

Mears

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

132

135

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We perform a multimodel detection and attribution study with climate model simulation output and satellite-based measurements of tropospheric and stratospheric temperature change. We use simulation output from 20 climate models participating in phase 5 of the Coupled Model Intercomparison Project. This multimodel archive provides estimates of the signal pattern in response to combined anthropogenic and natural external forcing (the fingerprint) and the noise of internally generated variability. Using these estimates, we calculate signal-to-noise (S/N) ratios to quantify the strength of the fingerprint in the observations relative to fingerprint strength in natural climate noise. For changes in lower stratospheric temperature between 1979 and 2011, S/N ratios vary from 26 to 36, depending on the choice of observational dataset. In the lower troposphere, the fingerprint strength in observations is smaller, but S/N ratios are still significant at the 1% level or better, and range from three to eight. We find no evidence that these ratios are spuriously inflated by model variability errors. After removing all global mean signals, model fingerprints remain identifiable in 70% of the tests involving tropospheric temperature changes. Despite such agreement in the large-scale features of model and observed geographical patterns of atmospheric temperature change, most models do not replicate the size of the observed changes. On average, the models analyzed underestimate the observed cooling of the lower stratosphere and overestimate the warming of the troposphere. Although the precise causes of such differences are unclear, model biases in lower stratospheric temperature trends are likely to be reduced by more realistic treatment of stratospheric ozone depletion and volcanic aerosol forcing.climate change detection and attribution | climate modeling | multimodel analysis P attern-based fingerprint studies seek to elucidate the complex causes of historical climate change (1-9). An initial focus of fingerprint research was on the vertical structure of atmospheric temperature changes (3,5,7,(10)(11)(12)(13)(14)(15). This work indicated that natural external forcings, such as volcanic eruptions and solar variability, produce atmospheric temperature fingerprints that differ from the fingerprints of human-caused changes in greenhouse gases or aerosols (3,11,16). Fingerprinting with atmospheric temperature changes has provided strong scientific evidence of a discernible human influence on global climate (17)(18)(19).Most fingerprint studies involving atmospheric temperature have relied on individual models, with relatively little consideration of how results are affected by model and observational uncertainty. The key model uncertainties are in the anthropogenic and natural external forcings (20), the climate responses to these forcings, and the estimates of internal variability (17)(18)(19). Uncertainties in observations of atmospheric temperature change arise because of the different choices analysts make in adjusting raw mea...

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“…Model simulations provide a way to help elucidate the link between climate variability and sea-ice variability and trends. As previous studies have suggested that the Southern Annular Mode (SAM) 21,22 , the El Niño Southern Oscillation (ENSO) 23,23 and the weather 24,25 may all be important factors in sea-ice variability and trends, a study to assess the dominant drivers is needed.…”

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confidence: 99%

Sources of heterogeneous variability and trends in Antarctic sea-ice

et al. 2015

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While the Northern Hemisphere sea-ice has uniformly declined over the past several decades, the observed sea-ice in the Southern Hemisphere has exhibited regions of increase and decrease. Here we use a comprehensive set of ocean-sea-ice simulations (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007) to elucidate the drivers of the observed heterogeneous sea-ice trends. We show wind variability is an important determinant of the heterogeneous pattern of the variability and trends in Southern Hemisphere sea-ice. Only in the West Pacific region does Southern Annular Mode wind forcing contribute significantly to the trend in sea-ice duration. El Niño Southern Oscillation wind forcing contribution to the sea-ice duration trend is confined to the Atlantic and Pacific. In the Indian Ocean, weather is a significant driver of the sea-ice duration trend. Only in the East Pacific region is wind forcing alone insufficient to give rise to the observed sea-ice decline and must be augmented by warming to reproduce the observations.

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Consistent past half-century trends in the atmosphere, the sea ice and the ocean at high southern latitudes

Cited by 89 publications

References 74 publications

An assessment and interpretation of the observed warming of West Antarctica in the austral spring

An assessment and interpretation of the observed warming of West Antarctica in the austral spring

Identifying human influences on atmospheric temperature

Sources of heterogeneous variability and trends in Antarctic sea-ice

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