Pleistocene Sea-Level and Glacial Fluctuations, Coastal Ahklun Mountains, Southwest Alaska

最近在阿拉斯加西海岸南部（东布里斯托尔湾，北纬59年）的研究表明，冰川在更新世晚期经历了广泛的进展。另一方面，在阿拉斯加西北部（西元65年的苏厄德半岛和西元67年的布鲁克斯山脉），早期的威斯康辛冰川被限制在最高的山谷中，所占的面积大约比更新世中期和早期的进展要小一个数量级。最近一次冰川向阿拉斯加西南部海岸移动的时间，比上一次冰川向阿拉斯加西北部海岸移动的时间至少年轻30万年。为了理解这种明显的冰川地质和古气候不一致的原因和意义，必须解决以下问题：(1)在布里斯托尔湾东部和苏厄德半岛之间的海岸上，晚更新世冰川高峰和中更新世冰川高峰之间的交叉发生在什么地方和多远的地方？(2)不同源区的冰量在多大程度上受河谷地貌控制？(3)威斯康辛州晚期和威斯康辛州晚期前冰的地理分布对平衡线海拔（ELA）下降和平衡线海拔（ELA）梯度，从而对水分来源和其他气候变量有何影响？要解决这些问题，需要在布里斯托尔湾东部和苏厄德半岛之间唯一的冰川地区——阿克伦山脉进行广泛的实地考察、航空摄影和地质年代学研究。这将取决于多学科的努力，以获得对矿床的数字年龄控制。最先进的地质年代学和沉积学技术将被应用于重建更新世海平面和冰川波动的时空格局。这项工作将提高对阿拉斯加西部冰川的古气候控制及其与全球气候系统的关系的理解；应该能够解决阿拉斯加西南部的冰川化是否与北半球冰盖波动同步，或者这里的主要冰川化是否先于低纬度的冰积聚。

Recent work in the south part of the west coast of Alaska (eastern Bristol Bay, 59oN) demonstrates that glaciers experienced extensive advances during the late Pleistocene. In northwestern Alaska (Seward Peninsula, 65oN, and western Brooks Range, 67oN), on the other hand, early Wisconsin glaciers were restricted to the highest mountain valleys and occupied an area approximately an order of magnitude less extensive than during middle and early Pleistocene advances. The most-recent major advance of glacier ice to the coast in southwestern Alaska was at least 300,000 yr younger than the last advance of ice to the coast in northwestern Alaska. To understand the cause and significance of this apparent glacial- geologic and paleoclimatological incongruity, the following must be addressed: (1) Where and over what distance along the coast between eastern Bristol Bay and Seward Peninsula does the cross-over between late Pleistocene glacial maxima and middle Pleistocene maxima occur? (2) To what extent to valley hypsometries control the extent of ice from the different source areas? (3) What does the geographic distribution of late-Wisconsin and pre-late-Wisconsin ice imply about equilibrium line altitude (ELA) lowering and equilibrium line altitude (ELA) gradients, and consequently, moisture sources and other climate variables? Solving these questions will require extensive field, aerial photographic, and geochronologic research in the only glaciated region between eastern Bristol Bay and Seward Peninsula-the Ahklun Mountains. It will depend on a multi-disciplinary effort to obtain numerical-age control on the deposits. State-of-the-art geochronologic and sedimentologic techniques will be applied to reconstruct the spatial and temporal pattern of Pleistocene sea-level and glacier fluctuations. This work will improve the understanding of the paleoclimatological controls of glaciation across western Alaska and their relation to the global climate system; should enable to address whether gl aciation in southwestern Alaska is synchronous with Northern Hemispheric ice-sheet fluctuations, or whether major glaciations here precedes ice build-up at lower latitude.