|
|
Glaciers have strongly contributed to sea-level rise during the past century and will continue to be an important part of the sea-level budget during the twenty-first century
. Here, we review the progress in estimating global glacier mass change from in situ measurements of mass and length changes, remote sensing methods, and mass balance modeling driven by climate observations. For the period before the onset of satellite observations, different strategies to overcome the uncertainty associated with monitoring only a small sample of the world’s glaciers have been developed. These methods now yield estimates generally reconcilable with each other within their respective uncertainty margins. Whereas this is also the case for the recent decades, the greatly increased number of estimates obtained from remote sensing reveals that gravimetry-based methods typically arrive at lower mass loss estimates than the other methods. We suggest that strategies for better interconnecting the different methods are needed to ensure progress and to increase the temporal and spatial detail of reliable glacier mass change estimates
Read More
|
|
|
Global climate change is primarily linked to changes in greenhouse gases, but land-cover change (LCC) has increasingly been recognized as another forcing on the regional scale
. The related effects on alpine glaciers are, however, not yet known. Here we present the first quantification of the contribution of LCC-driven atmospheric change to glacier mass loss, illustrated by the well-studied case of Kilimanjaro in tropical Africa. We employ a novel multi-scale modelling approach6, which links atmospheric dynamics and local glacier mass balance in a fully physical way and is validated by in situ measurements. Using different model settings, this shows that local LCC since the 1970s has contributed 7±6% (17±12%) to mass loss of a southern slope glacier in the dry (wet) season, but this effect could reverse in the other mountain sectors and also decrease glacier mass loss. Thus, for the moment, the hypothesis that local LCC is another forcing of glacier loss on Kilimanjaro cannot be corroborated. More generally, our results indicate that the impact of local LCC on mountain glaciers is constrained by regional circulation (moisture trajectories), altitude (distance to forest), and outside the tropics by precipitation mechanisms (frontal systems). We therefore argue that attribution of glacier change and variability to large-scale climate dynamics is unlikely to be distorted by local LCC
Read More
|
|
|
Although reliable figures are often missing, considerable detrimental changes due to shrinking glaciers are universally expected for water availability in river systems under the influence of ongoing global climate change
. We estimate the contribution potential of seasonally delayed glacier melt water to total water availability in large river systems. We find that the seasonally delayed glacier contribution is largest where rivers enter seasonally arid regions and negligible in the lowlands of river basins governed by monsoon climates. By comparing monthly glacier melt contributions with population densities in different altitude bands within each river basin, we demonstrate that strong human dependence on glacier melt is not collocated with highest population densities in most basins
Read More
|
email alert
or subscribe to the 
RSS feed.
