Snowfall was measured at 11 sites in the McMurdo Dry Valleys to determine its magnitude, its temporal changes, and spatial patterns. Annual values ranged from 3 to 50 mm water equivalent with the highest values nearest the coast and decreasing inland. A particularly strong spatial gradient exists in Taylor Valley, probably resulting from local uplift conditions at the coastal margin and valley topography that limits migration inland. More snow occurs in winter near the coast, whereas inland no seasonal pattern is discernable. This may be due, again, to local uplift conditions, which are common in winter. We find no influence of the distance to the sea ice edge. Katabatic winds play an important role in transporting snow to the valley bottoms and essentially double the precipitation. That much of the snow accumulation sublimates prior to making a hydrologic contribution underscores the notion that the McMurdo Dry Valleys are indeed an extreme polar desert.

[1] The cryoconite holes of the McMurdo Dry Valleys are simple, closed biogeochemical systems involving water, ice, mineral and organic debris, which serve as ecosystems for consortia of microorganisms. This study is the first to document the seasonal and annual chemical evolution of solutes in cryoconite holes. Samples of glacier ice, frozen cryoconite holes and those containing water were collected during the austral summer of [2005][2006]. The isolation age was calculated from the excess Cl À in the holes, and varied from 0 to 5 years (a), consistent with the last hot summer when the cryoconite holes were open to the atmosphere. The holes progressively deepen with isolation age. Variations in DIC, DOC, K + and SO 4 2À suggest that dissolution of primary minerals in the cryoconite debris, cyclical precipitation and dissolution of secondary carbonates, net photosynthesis over summer and net respiration during the autumnal freeze are the principal reactions which perturb the seasonal and annual solute concentrations in the holes. DOC is generated in the holes at a rate of 7.5 mg C cm À2 a À1 , and non-sea-salt K + accumulates in frozen holes at a rate of 0.073 meq cm À2 a À1 . We infer that C cycling is complex even in these otherwise simple systems.

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Abstract. Glacier fluctuations contribute to variations in sea level and historical glacier length fluctuations are natural indicators of past climate change. To study these subjects, long-term information of glacier change is needed. In this paper we present a data set of global long-term glacier length fluctuations. The data set is a compilation of available information on changes in glacier length worldwide, including both measured and reconstructed glacier length fluctuations. All 471 length series start before 1950 and cover at least four decades. The longest record starts in 1535, but the majority of time series start after 1850. The number of available records decreases again after 1962. The data set has global coverage including records from all continents. However, the Canadian Arctic is not represented in the data set. The available glacier length series show relatively small fluctuations until the mid-19th century, followed by a global retreat. The retreat was strongest in the first half of the 20th century, although large variability in the length change of the different glaciers is observed. During the 20th century, calving glaciers retreated more than land-terminating glaciers, but their relative length change was approximately equal. Besides calving, the glacier slope is the most important glacier property determining length change: steep glaciers have retreated less than glaciers with a gentle slope.

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