scholarly journals The changing shape of Northern Hemisphere summer temperature distributions

2016 ◽  
Vol 121 (15) ◽  
pp. 8849-8868 ◽  
Author(s):  
Karen A. McKinnon ◽  
Andrew Rhines ◽  
Martin P. Tingley ◽  
Peter Huybers

2016 ◽  
Vol 51 (3) ◽  
pp. 596-602
Author(s):  
Yui Sasaki ◽  
Kaoru Matsuo ◽  
Makoto Yokoyama ◽  
Masaru Sasaki ◽  
Takahiro Tanaka ◽  
...  


1995 ◽  
Vol 21 ◽  
pp. 111-116 ◽  
Author(s):  
Philippe Huybrechts ◽  
Stephen T’ Siobbel

A three-dimensional time-dependent thermomechanical ice-sheet model was used together with a two-level (snow-accumulation/runoff) mass-balance model to investigate the Quaternary ice sheets of the Northern Hemisphere. The model freely generates the ice-sheet geometry in response to specified changes in surface temperature and mass balance, and includes bedrock adjustment, basal sliding and a full temperature calculation within the ice. The mass-balance parameterization makes a distinction between snowfall and melting. Yearly snowfall rates depend on the present precipitation distribution, and are varied proportionally to changes in surface temperature and the moisture content of the air. The ablation model is based on the positive-degree-day method, and distinguishes between ice and snow melting. This paper discusses steady-slate characteristics, conditions for growth and retreat, and response time-scales of ice sheets as a function of a prescribed lowering of summer temperature. Most notably, the modelled extents of the Eurasian ice sheet for a summer temperature lowering of 6–7 K and of the Laurentide ice sheet for a cooling of 9–10 K are in reasonable agreement with most reconstructions based on geological evidence, except for the presence of a large ice sheet stretching from Alaska across the Bering Strait to most of eastern Siberia. In addition, wet basal conditions turned out to be always confined to the margin, whereas central areas in these reconstructions remained always cold-based. This is of relevance for processes involving reduced basal traction.



2015 ◽  
Vol 80 (717) ◽  
pp. 1073-1082
Author(s):  
Kaoru MATSUO ◽  
Takahiro TANAKA


2013 ◽  
Vol 118 (15) ◽  
pp. 8297-8305 ◽  
Author(s):  
Emily C. Gill ◽  
Thomas N. Chase ◽  
Roger A. Pielke ◽  
Klaus Wolter


Nature ◽  
10.1038/30943 ◽  
1998 ◽  
Vol 393 (6684) ◽  
pp. 450-455 ◽  
Author(s):  
K. R. Briffa ◽  
P. D. Jones ◽  
F. H. Schweingruber ◽  
T. J. Osborn


2011 ◽  
Vol 24 (23) ◽  
pp. 5998-6012 ◽  
Author(s):  
Justin J. Wettstein ◽  
Jeremy S. Littell ◽  
John M. Wallace ◽  
Ze’ev Gedalof

Abstract Patterns of correlation between tree rings and local temperature or precipitation are investigated using 762 International Tree-Ring Data Bank standardized ring width site chronology time series, and a gridded dataset of temperature and precipitation. Coherent regional- and, in some cases, hemispheric-scale patterns of correlation are found in the extratropical Northern Hemisphere for both the summer prior to and the summer concurrent with ring width formation across different species and over large distances. Among those chronologies that are primarily linked to temperature, thicker ring widths are generally associated with anomalously cool prior summer temperature and anomalously warm concurrent summer temperature. Reconstructions of local summer temperature using prior, concurrent, and/or subsequent year ring widths as predictors demonstrate that useful climate–growth information generally exists in ring widths that are both concurrent with and subsequent to the summer temperature anomaly. Consistent prior summer temperature–ring width relationships have received relatively little previous attention. Among those chronologies that are primarily linked to precipitation, thicker ring widths are generally associated with high summer precipitation in both the year prior to and the year concurrent with ring formation. The magnitude and spatial consistency of temperature correlations are greater than those for precipitation, at least on the hemispheric scale. These results support and serve to generalize the conclusions of prior regionally restricted and/or species-specific studies relating ring width to energy and/or water limitations. Regional- and hemispheric-scale patterns of ring width–temperature or ring width–precipitation correlations show up more clearly in species-specific and frequency-dependent analyses. Different species respond differently to temperature and precipitation anomalies. Consistent with the hemispheric patterns described above, most standardized ring width time series more faithfully record the high frequency component of the temperature signal than the low frequency component. The potential for enhanced coherence in regionally restricted, species-specific, and frequency-dependent analyses is independently verified by examining the correlation between ring width time series over geographical distance. This broader characterization of relationships between tree-ring widths and local climate provides an objective basis for selecting tree ring or other similarly high-resolution proxy data for regional-, hemispheric-, or global-scale paleoclimate reconstructions.



1995 ◽  
Vol 21 ◽  
pp. 111-116 ◽  
Author(s):  
Philippe Huybrechts ◽  
Stephen T’ Siobbel

A three-dimensional time-dependent thermomechanical ice-sheet model was used together with a two-level (snow-accumulation/runoff) mass-balance model to investigate the Quaternary ice sheets of the Northern Hemisphere. The model freely generates the ice-sheet geometry in response to specified changes in surface temperature and mass balance, and includes bedrock adjustment, basal sliding and a full temperature calculation within the ice. The mass-balance parameterization makes a distinction between snowfall and melting. Yearly snowfall rates depend on the present precipitation distribution, and are varied proportionally to changes in surface temperature and the moisture content of the air. The ablation model is based on the positive-degree-day method, and distinguishes between ice and snow melting. This paper discusses steady-slate characteristics, conditions for growth and retreat, and response time-scales of ice sheets as a function of a prescribed lowering of summer temperature. Most notably, the modelled extents of the Eurasian ice sheet for a summer temperature lowering of 6–7 K and of the Laurentide ice sheet for a cooling of 9–10 K are in reasonable agreement with most reconstructions based on geological evidence, except for the presence of a large ice sheet stretching from Alaska across the Bering Strait to most of eastern Siberia. In addition, wet basal conditions turned out to be always confined to the margin, whereas central areas in these reconstructions remained always cold-based. This is of relevance for processes involving reduced basal traction.



2018 ◽  
Vol 83 (751) ◽  
pp. 769-779 ◽  
Author(s):  
Yui SASAKI ◽  
Kaoru MATSUO ◽  
Makoto YOKOYAMA ◽  
Takahiro TANAKA ◽  
Satoru SADOHARA


2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg & Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg & Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).



2000 ◽  
Vol 179 ◽  
pp. 303-306
Author(s):  
S. D. Bao ◽  
G. X. Ai ◽  
H. Q. Zhang

AbstractWe compute the signs of two different current helicity parameters (i.e., αbestandHc) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative αbestand 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameterHcshows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.



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