Editorial Type:
Article
Article Type:
Research Article

Midlatitude Moisture Contribution to Recent Arctic Tropospheric Summertime Variability

Frédéric Laliberté Department of Physics, University of Toronto, Toronto, Ontario, Canada

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Paul J. Kushner Department of Physics, University of Toronto, Toronto, Ontario, Canada

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Print Publication:
01 Aug 2014
DOI:
https://doi.org/10.1175/JCLI-D-13-00721.1
Page(s):
5693–5707
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Abstract

The dynamics of late summer Arctic tropospheric heat content variability is studied using reanalyses. In both trends and interannual variability, much of the August heat content variability in the Arctic midtroposphere can be explained by the total—sensible plus latent—heat content variability at the midlatitude near surface in July. Climate models suggest that this connection is part of the global warming signal in September–November, but in reanalyses the connection is most strongly present in July–August variability and trends. It is argued that heat content signals are propagated from the midlatitude near surface to the Arctic midtroposphere approximately along climatological moist isentropes. High-frequency data reveal that the propagating signal is primarily driven by a few strong meridional heat flux events each summer season. Composite analysis on these events shows that August meridional heat fluxes into the Arctic midtroposphere are succeeded by positive heat content anomalies in the lower troposphere a few days later. This second connection between the Arctic midtroposphere and the Arctic lower troposphere could be sufficient to explain some of the recent Arctic 850-hPa temperature variability north of 75°N.

Supplemental information related to this paper is available at the Journals Online website: http://dx.doi.org/10.1175/JCLI-D-13-00721.s1.

Corresponding author address: Frédéric Laliberté, Department of Physics, University of Toronto, 60 St. George Street, Toronto ON M5S 1A7, Canada. E-mail: frederic.laliberte@utoronto.ca

Abstract

The dynamics of late summer Arctic tropospheric heat content variability is studied using reanalyses. In both trends and interannual variability, much of the August heat content variability in the Arctic midtroposphere can be explained by the total—sensible plus latent—heat content variability at the midlatitude near surface in July. Climate models suggest that this connection is part of the global warming signal in September–November, but in reanalyses the connection is most strongly present in July–August variability and trends. It is argued that heat content signals are propagated from the midlatitude near surface to the Arctic midtroposphere approximately along climatological moist isentropes. High-frequency data reveal that the propagating signal is primarily driven by a few strong meridional heat flux events each summer season. Composite analysis on these events shows that August meridional heat fluxes into the Arctic midtroposphere are succeeded by positive heat content anomalies in the lower troposphere a few days later. This second connection between the Arctic midtroposphere and the Arctic lower troposphere could be sufficient to explain some of the recent Arctic 850-hPa temperature variability north of 75°N.

Supplemental information related to this paper is available at the Journals Online website: http://dx.doi.org/10.1175/JCLI-D-13-00721.s1.

Corresponding author address: Frédéric Laliberté, Department of Physics, University of Toronto, 60 St. George Street, Toronto ON M5S 1A7, Canada. E-mail: frederic.laliberte@utoronto.ca

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