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Rosalyn K. Hayward 《地球表面变化过程与地形》2011,36(14):1967-1972
The Mars Global Digital Dune Database (MGD3) now extends from 90°N to 65°S. The recently released north polar portion (MC‐1) of MGD3 adds ~844 000 km2 of moderate‐ to large‐size dark dunes to the previously released equatorial portion (MC‐2 to MC‐29) of the database. The database, available in GIS‐ and tabular‐format in USGS Open‐File Reports, makes it possible to examine global dune distribution patterns and to compare dunes with other global data sets (e.g. atmospheric models). MGD3 can also be used by researchers to identify areas suitable for more focused studies. The utility of MGD3 is demonstrated through three example applications. First, the uneven geographic distribution of the dunes is discussed and described. Second, dune‐derived wind direction and its role as ground truth for atmospheric models is reviewed. Comparisons between dune‐derived winds and global and mesoscale atmospheric models suggest that local topography may have an important influence on dune‐forming winds. Third, the methods used here to estimate north polar dune volume are presented and these methods and estimates (1130 km3 to 3250 km3) are compared with those of previous researchers (1158 km3 to 15 000 km3). In the near future, MGD3 will be extended to include the south polar region. Published in 2011. This article is a US Government work and is in the public domain in the USA. 相似文献
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Scales of recruitment variability in warming waters: Comparing native and introduced oysters in Hood Canal,Washington, USA
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The effect of climate change on natural oyster recruitment has the potential to disrupt many of the ecosystem services oysters provide. Due to the temperature‐sensitivity of reproduction, oyster recruitment may shift as water temperatures rise. A biological imprint of climate change was revealed in a multi‐decadal time series of recruitment of non‐native Pacific oysters (Crassostrea gigas) in the main stem of Hood Canal, Washington, USA, extracted from historic fishery documents. Water in July and August warmed significantly from 1945 to 1995 (0.028 ± 0.004°C per year [±SE]) and accounted for an increase in Pacific oyster recruitment (7% per year, 0.028 ± 0.006 spat per year on log scale [±SE]); recruitment also strongly tracked inter‐annual variability in summer water temperature. Methods used to collect historical data were repeated in 2013–2015 when recruitment of both Pacific oysters and native Olympia oysters (Ostrea lurida) were recorded in main stem and lower Hood Canal. Both historic and modern data show large variation within and between years for temperature as well as recruitment. The modern data add information regarding spatial variation, in that recruitment patterns in the two regions of Hood Canal were decoupled. As temperatures continue to increase, non‐native Pacific oysters are likely to be favored over Olympia oysters, which recruit earlier at lower temperatures and presently contribute less than half of total oyster recruits. Future recruitment, however, may be limited by environmental factors other than temperature, a point indicated particularly in Hood Canal where many subtidal species already respond strongly to gradients in dissolved oxygen. 相似文献
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