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surface temperature trends through circulation-driven thermal and dynamical impacts ( Holland and Kwok 2012 ; Ding et al. 2014 ). In contrast to the observed trends, the CMIP5 and five model large ensemble mean linear trends under the increase of CO 2 forcing and ozone depletion over the same period (1979–2017) show uniform warming everywhere with slightly larger height rise in the tropics at upper levels (e.g., Z200; Figs. 1b,c ), reflecting a temperature response to anthropogenic forcing expected
surface temperature trends through circulation-driven thermal and dynamical impacts ( Holland and Kwok 2012 ; Ding et al. 2014 ). In contrast to the observed trends, the CMIP5 and five model large ensemble mean linear trends under the increase of CO 2 forcing and ozone depletion over the same period (1979–2017) show uniform warming everywhere with slightly larger height rise in the tropics at upper levels (e.g., Z200; Figs. 1b,c ), reflecting a temperature response to anthropogenic forcing expected
1. Introduction Improving our understanding of the dynamics of the atmosphere–ocean–sea ice system and the connecting mechanisms between the high and low latitudes has become increasingly important to climate science in the face of a rapidly warming world. The polar regions and the cryosphere in both hemispheres are active components in global climate. For example, changes within the polar regions dictate the strength of the thermal gradient between the tropics and the poles. Climate changes
1. Introduction Improving our understanding of the dynamics of the atmosphere–ocean–sea ice system and the connecting mechanisms between the high and low latitudes has become increasingly important to climate science in the face of a rapidly warming world. The polar regions and the cryosphere in both hemispheres are active components in global climate. For example, changes within the polar regions dictate the strength of the thermal gradient between the tropics and the poles. Climate changes
ASL in austral autumn, although the latter study only observed this in coupled climate model simulations, and the response was weaker than that in austral summer. Other studies linked ASL-related trends in the regional atmospheric circulation to changes in the tropics ( Ding et al. 2011 ; Ding and Steig 2013 ). In Ding et al. (2011) , warming of the central tropical Pacific in austral winter generated a Rossby wave train that led to higher geopotential heights in the Amundsen Sea, which
ASL in austral autumn, although the latter study only observed this in coupled climate model simulations, and the response was weaker than that in austral summer. Other studies linked ASL-related trends in the regional atmospheric circulation to changes in the tropics ( Ding et al. 2011 ; Ding and Steig 2013 ). In Ding et al. (2011) , warming of the central tropical Pacific in austral winter generated a Rossby wave train that led to higher geopotential heights in the Amundsen Sea, which
: Teleconnections between tropical Pacific SST anomalies and extratropical Southern Hemisphere climate . J. Climate , 28 , 56 – 65 , doi: 10.1175/JCLI-D-14-00438.1 . Clem , K. R. , and R. L. Fogt , 2015 : South Pacific circulation changes and their connection to the tropics and regional Antarctic warming in austral spring, 1979–2012 . J. Geophys. Res. Atmos. , 120 , 2773 – 2792 , doi: 10.1002/2014JD022940 . Clem , K. R. , and J. A. Renwick , 2015 : Austral spring Southern Hemisphere
: Teleconnections between tropical Pacific SST anomalies and extratropical Southern Hemisphere climate . J. Climate , 28 , 56 – 65 , doi: 10.1175/JCLI-D-14-00438.1 . Clem , K. R. , and R. L. Fogt , 2015 : South Pacific circulation changes and their connection to the tropics and regional Antarctic warming in austral spring, 1979–2012 . J. Geophys. Res. Atmos. , 120 , 2773 – 2792 , doi: 10.1002/2014JD022940 . Clem , K. R. , and J. A. Renwick , 2015 : Austral spring Southern Hemisphere
, outweighing the thermodynamically induced warming from Arctic sea ice loss. While most of the climate impacts from Arctic sea ice loss are expected to occur at middle and high latitudes, recent work has shown that ocean–atmosphere coupling may extend the reach of these impacts into the tropics and Southern Hemisphere ( D15 ). The dynamical ocean response, in particular, plays a key role in communicating the effects of Arctic sea ice loss to the entire globe via a weakening of the northward oceanic heat
, outweighing the thermodynamically induced warming from Arctic sea ice loss. While most of the climate impacts from Arctic sea ice loss are expected to occur at middle and high latitudes, recent work has shown that ocean–atmosphere coupling may extend the reach of these impacts into the tropics and Southern Hemisphere ( D15 ). The dynamical ocean response, in particular, plays a key role in communicating the effects of Arctic sea ice loss to the entire globe via a weakening of the northward oceanic heat
1. Introduction The Madden–Julian oscillation (MJO) is the dominant mode of intraseasonal atmospheric variability in the tropics ( Madden and Julian 1971 , 1972 ), characterized by a horizontally large-scale (10 3 –10 4 km) pattern of atmospheric convection and circulation that propagates eastward along the equator with a time scale of 30–90 days ( Zhang 2005 ). Numerous efforts have been made to understand and to better predict this phenomenon. One of the reasons is because the MJO has a
1. Introduction The Madden–Julian oscillation (MJO) is the dominant mode of intraseasonal atmospheric variability in the tropics ( Madden and Julian 1971 , 1972 ), characterized by a horizontally large-scale (10 3 –10 4 km) pattern of atmospheric convection and circulation that propagates eastward along the equator with a time scale of 30–90 days ( Zhang 2005 ). Numerous efforts have been made to understand and to better predict this phenomenon. One of the reasons is because the MJO has a
depletion, were the main cause of zonally symmetric circulation trends in the SH during the twentieth century ( Staten et al. 2012 ). As with the response to ozone depletion, there is no consensus on the most important mechanisms of the response to tropical warming ( Vallis et al. 2014 ). The prevailing argument is that the rising SSTs lead to a meridionally broad, midtropospheric warming in the tropics, which alters the meridional temperature gradient, pushing the latitude of baroclinicity poleward
depletion, were the main cause of zonally symmetric circulation trends in the SH during the twentieth century ( Staten et al. 2012 ). As with the response to ozone depletion, there is no consensus on the most important mechanisms of the response to tropical warming ( Vallis et al. 2014 ). The prevailing argument is that the rising SSTs lead to a meridionally broad, midtropospheric warming in the tropics, which alters the meridional temperature gradient, pushing the latitude of baroclinicity poleward
in this season despite the fact that quasi-stationary Rossby waves would be most favored in winter ( Jin and Hoskins 1995 ). Moreover, Pacific sea ice and the Southern Oscillation index covary synchronously in SON but not in other seasons ( Simmonds and Jacka 1995 ). Therefore, we focus our investigation over SON. In addition, Rossby wave activity flux as described by Takaya and Nakamura (2001) is computed to investigate the Rossby wave propagation from the tropics. This is a diagnostic tool
in this season despite the fact that quasi-stationary Rossby waves would be most favored in winter ( Jin and Hoskins 1995 ). Moreover, Pacific sea ice and the Southern Oscillation index covary synchronously in SON but not in other seasons ( Simmonds and Jacka 1995 ). Therefore, we focus our investigation over SON. In addition, Rossby wave activity flux as described by Takaya and Nakamura (2001) is computed to investigate the Rossby wave propagation from the tropics. This is a diagnostic tool
p < 0.05 level are boldface and at p < 0.01 are boldface and italicized. Significance is calculated following a Student’s two-tailed t test. During MAM, the SAM pattern alone dominates variability in PC1, with nearly 50% of the PC1 variance explained by the SAM index. During JJA and SON, PC1 is significantly correlated with both the SAM index and tropical Pacific SSTs, although the correlations with the SAM are consistently stronger than with the tropics. Therefore the SAM pattern alone
p < 0.05 level are boldface and at p < 0.01 are boldface and italicized. Significance is calculated following a Student’s two-tailed t test. During MAM, the SAM pattern alone dominates variability in PC1, with nearly 50% of the PC1 variance explained by the SAM index. During JJA and SON, PC1 is significantly correlated with both the SAM index and tropical Pacific SSTs, although the correlations with the SAM are consistently stronger than with the tropics. Therefore the SAM pattern alone
convection in the central equatorial Pacific ( Mo and Peagle 2001 ; Harangozo 2004 ; Lachlan-Cope and Connolley 2006 ), with location and intensity being the key forcing for the high-latitude blocking events. Dynamically, Seager et al. (2003) described a mechanism different from the Rossby wave interaction on SH circulation whereby an El Niño event warms the tropics and strengthens the Hadley circulation and subtropical jet (STJ). This phenomenon modifies the meridional circulation by diverting
convection in the central equatorial Pacific ( Mo and Peagle 2001 ; Harangozo 2004 ; Lachlan-Cope and Connolley 2006 ), with location and intensity being the key forcing for the high-latitude blocking events. Dynamically, Seager et al. (2003) described a mechanism different from the Rossby wave interaction on SH circulation whereby an El Niño event warms the tropics and strengthens the Hadley circulation and subtropical jet (STJ). This phenomenon modifies the meridional circulation by diverting
