Temporal and spatial variability in coastline response to declining sea-ice in northwest Alaska
Temporal and spatial variability in coastline response to declining sea-ice in northwest Alaska
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DOI：
10.1016/j.margeo.2018.07.007
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发表时间：
2018-10-01
期刊：
影响因子：
2.9
通讯作者：
Jordan, J. W.
中科院分区：
文献类型：
--
作者：
Farquharson, L. M.;Mann, D. H.;Jordan, J. W.
北极海冰的范围正在缩小，使海岸线面临更多风暴波事件的影响。迫切需要了解这些变化如何影响北极沿岸的地貌过程。在这里，我们描述了过去 64 年中楚科奇海海岸线两个地貌不同、风暴波主导的河段海岸线变化的空间和时间模式。其中一个研究区域包括克鲁森斯坦角 (CAKR) 面向西至西南的粗碎屑海岸线和富含冰的悬崖。另一个覆盖了白令陆桥国家公园 (BELA) 内朝北的障壁岛沙质海岸线、富含冰的悬崖和埃斯彭伯格角沙嘴。这两个研究区域均位于连续的永久冻土带内，该永久冻土带既存在于陆地上，也存在于近海，并以富含冰的断崖形式露头于 BELA 海岸。我们利用航空和卫星图像绘制了三个观测时期沿海地貌的变化：1950-1980 年、1980-2003 年和 2003-2014 年。然后，我们将这些地貌变化与海冰覆盖范围的变化进行了比较，1979 年至 2016 年间，楚科奇海南部的海冰覆盖范围每十年减少 10 天。在研究期间，BELA 和 CAKR 沿海地貌的变化表现出高度的空间变异性。 2003年至2014年间，BELA障壁岛海岸线的平均变化率最高，为-1.5 m yr(-1)，而CAKR粗糙的弹性障壁海滩仅显示出最小的变化。总体而言，大约 10 年后，BELA 和 CAKR 的海岸线变得更加动态（侵蚀增加或堆积增加）。 2003 年，海岸线变化的空间变异性在第一个观测期（1950-1980 年）和最后一个观测期（2003-2014 年）之间大致翻了一番。沿海活力的增加可能标志着一个过渡时期，导致这些受冰影响的海岸线出现新的地貌平衡状态。
Arctic sea-ice is declining in extent, leaving coastlines exposed to more storm-wave events. There is an urgent need to understand how these changes affect geomorphic processes along Arctic coasts. Here we describe spatial and temporal patterns of shoreline changes along two geomorphologically distinct, storm-wave dominated reaches of the Chukchi Sea coastline over the last 64 years. One study area encompasses the west- to southwest facing, coarse-clastic shoreline and ice-rich bluffs of Cape Krusenstem (CAKR). The other covers the north facing, sandy shorelines on barrier islands, ice-rich bluffs, and the Cape Espenberg spit in the Bering Land Bridge National Park (BELA). Both study areas lie within the zone of continuous permafrost, which exists both on and offshore and outcrops as ice-rich bluffs along the BELA coast. We mapped changes in coastal geomorphology over three observation periods: 1950-1980, 1980-2003, and 2003-2014 using aerial and satellite imagery. We then compared these geomorphic changes to changes in sea-ice coverage, which declined similar to 10 days per decade between 1979 and 2016 in the southern Chukchi Sea. Changes in coastal geomorphology in both BELA and CAKR exhibited high spatial variability over the study period. Between 2003 and 2014, shorelines of barrier islands in BELA exhibited the highest mean rates of change, -1.5 m yr(-1), while coarse, elastic barrier beaches in CAKR showed only minimal change. Overall, shorelines in both BELA and CAKR became more dynamic (increasing erosion or increasing accumulation) after ca. 2003, with spatial variability in shoreline changes roughly doubling between the first period of observation (1950-1980) and the last (2003-2014). This increase in coastal dynamism may signal a transitional period leading to new state of geomorphic equilibria along these ice-affected coastlines.