Hraðari bráðnun jökla í Sviss fyrir 60 árum en undanfarið...

 

 

Á vef ETH í Zurich er grein sem nefnist  The stupefying pace of glacier melt in the 1940s. 

Þar er fjallað um nýja grein frá 3ja des. s.l. í ritrýndu timariti Geophysical Research Letters (GRL) sem nefnist  Strong Alpine glacier melt in the 1940s due to enhanced solar radiation. Sjá samantekt hér.

 

Í greininni kemur fram að bráðnun jökla í Sviss hafi verið hraðari á fimmta áratug síðustu aldar en í dag, þrátt fyrir hlýindi undanfarinna ára. Um miðja síðustu öld var vissulega einnig hlýtt, en höfundar greinarinnar kenna um breytingum í inngeislun sólar og vísa þá til breytilegs magn loftborinna agna (aerosols) og skýja.

 

Í samantektinni (abstract) á vef  GRL stendur:

 

"A 94-year time series of annual glacier melt at four high elevation sites in the European Alps is used to investigate the effect of global dimming and brightening of solar radiation on glacier mass balance. Snow and ice melt was stronger in the 1940s than in recent years, in spite of significantly higher air temperatures in the present decade. An inner Alpine radiation record shows that in the 1940s global shortwave radiation over the summer months was 8% above the long-term average and significantly higher than today, favoring rapid glacier mass loss. Dimming of solar radiation from the 1950s until the 1980s is in line with reduced melt rates and advancing glaciers".

 

Í inngangi (introduction) greinarinnar stendur: 

 

"[2]   Changes in climatic forcing are directly reflected by the mass budget of snow and ice surfaces (see von Hann [1897] and Hock [2005] for a review). Understanding the impact of changing climate conditions on glacier melt is a prerequisite for projections of glacier volume, changes in mountain hydrology, natural hazard frequency and sea level rise. For the last decades a rapid mass loss of mountain glaciers in response to climate warming has been reported for high and low latitudes all over the planet [Kaser et al., 2006]. Glacier wastage in the 20th century was mainly attributed to changes in air temperature [e.g., Haeberli and Beniston, 1998; Braithwaite and Zhang, 1999]. Global solar radiation at the earth's surface shows significant variations over the last century profoundly affecting the climate system [Ohmura and Lang, 1989; Wild et al., 2004, 2005]. Changes in solar radiation were rarely considered to explain cryospheric variability on decadal time scales [Ohmura et al., 2007]. This is due to the scarcity of both long-term radiation measurements and unbiased time series of glacier melt.

[3]   Here, we interpret a 94-year time series of annual snow and ice melt at four high elevation sites in the European Alps derived from the longest direct observations of glacier surface mass balance worldwide [Huss and Bauder, 2009]. We investigate possible drivers of multidecadal changes in the glacier mass budget by putting into context the impact of variations in solar radiation given by a 73-year radiation record. Based on the presented data sets we discuss the limitations of the empirical temperature-index approach for projections of glacier melt".

 

 

Myndin hér fyrir neðan er úr greininni sem bloggarinn á.  Ekki er heimilt að birta alla greinina hér.

 

Efri myndin sýnir frávik í bráðnun jökla. Á árunum 1942-1952 er hún 17% yfir meðaltali, en rúm 13% yfir meðaltali á árunum 199-2008.

 

Neðri myndin sýnir frávik í sólgeislun í wöttum á fermetra.

 

 

 Figure 3.

 

(a) Four-site average of annual melt anomaly n (see text) and sum of daily air temperatures above 0°C over the year at the study sites (dashed), low-pass filtered using 11-year running means.

 Melt anomalies for extreme decadal periods are shown by bars.

 

(b) JJA anomaly in measured global radiation at Davos. Period means are given.

 

 Sjá frétt á vef ETH hér: The stupefying pace of glacier melt in the 1940s.

 

 

 

 Huss M, Funk M & Ohmura A: Strong Alpine glacier melt in the 1940s due to enhanced solar radiation. Geophysical Research Letters (2009), 36, L23501, doi:10.1029/2009GL040789