A multidecadal-scale tropically-driven global teleconnection over the past millennium and its recent strengthening

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  • 1 Key Laboratory of Meteorological Disaster, Ministry of Education, Nanjing University of Information Science and Technology, Nanjing, China
  • 2 Department of Geography, and Earth Research Institute, University of California, Santa Barbara, Santa Barbara, California, USA
  • 3 Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, Shanghai, China
  • 4 Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
  • 5 Bren School of Environmental Science and Management, University of California, Santa Barbara, Santa Barbara, Los Angeles, California, USA
  • 6 Department of Earth Sciences, University of Southern California, California, USA
  • 7 Department of Atmospheric and Oceanic Sciences, Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, Los Angeles, California, USA
  • 8 Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University for Information Science and Technology, Nanjing, China
  • 9 Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
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Abstract

In the past 40 years, the global annual mean surface temperature has experienced a non-uniform warming, differing from the spatially uniform warming simulated by the forced responses of large multi-model ensembles to anthropogenic forcing. Rather, it exhibits significant asymmetry between the Arctic and Antarctic, intermittent and spatially varying warming trends along the Northern Hemisphere (NH) mid-latitudes and a slight cooling in the tropical eastern Pacific. In particular, this “wavy” pattern of temperature changes over the NH mid-latitudes features strong cooling over Eurasia in boreal winter. Here, we show that these non-uniform features of surface temperature changes are likely tied together by tropical eastern Pacific sea surface temperatures (SSTs), via a global atmospheric teleconnection. Using six reanalyses, we find that this teleconnection can be consistently obtained as a leading circulation mode in the past century. This tropically-driven teleconnection is associated with a Pacific SST pattern resembling the Interdecadal Pacific Oscillation (IPO), and hereafter referred to as the IPO-related Bipolar Teleconnection (IPO-BT). Further, two paleo-reanalysis reconstruction datasets show that the IPO-BT is a robust recurrent mode over the past 400 and 2000 years. The IPO-BT mode may thus serve as an important internal mode that regulates high-latitude climate variability on multidecadal time scales, favoring a warming (cooling) episode in the Arctic accompanied by cooling (warming) over Eurasia and the Southern Ocean (SO). Thus, the spatial non-uniformity of recent surface temperature trends may be partially explained by the enhanced appearance of the IPO-BT mode by a transition of the IPO toward a cooling phase in the eastern Pacific in the past decades.

This article is included in the Connecting the Tropics to the Polar Regions Special Collection.

Corresponding author (qinghua@ucsb.edu)

Abstract

In the past 40 years, the global annual mean surface temperature has experienced a non-uniform warming, differing from the spatially uniform warming simulated by the forced responses of large multi-model ensembles to anthropogenic forcing. Rather, it exhibits significant asymmetry between the Arctic and Antarctic, intermittent and spatially varying warming trends along the Northern Hemisphere (NH) mid-latitudes and a slight cooling in the tropical eastern Pacific. In particular, this “wavy” pattern of temperature changes over the NH mid-latitudes features strong cooling over Eurasia in boreal winter. Here, we show that these non-uniform features of surface temperature changes are likely tied together by tropical eastern Pacific sea surface temperatures (SSTs), via a global atmospheric teleconnection. Using six reanalyses, we find that this teleconnection can be consistently obtained as a leading circulation mode in the past century. This tropically-driven teleconnection is associated with a Pacific SST pattern resembling the Interdecadal Pacific Oscillation (IPO), and hereafter referred to as the IPO-related Bipolar Teleconnection (IPO-BT). Further, two paleo-reanalysis reconstruction datasets show that the IPO-BT is a robust recurrent mode over the past 400 and 2000 years. The IPO-BT mode may thus serve as an important internal mode that regulates high-latitude climate variability on multidecadal time scales, favoring a warming (cooling) episode in the Arctic accompanied by cooling (warming) over Eurasia and the Southern Ocean (SO). Thus, the spatial non-uniformity of recent surface temperature trends may be partially explained by the enhanced appearance of the IPO-BT mode by a transition of the IPO toward a cooling phase in the eastern Pacific in the past decades.

This article is included in the Connecting the Tropics to the Polar Regions Special Collection.

Corresponding author (qinghua@ucsb.edu)
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