Effects of submarine groundwater discharge on the present-day extent of relict submarine permafrost and gas hydrate stability on the Beaufort Sea continental shelf
Effects of submarine groundwater discharge on the present-day extent of relict submarine permafrost and gas hydrate stability on the Beaufort Sea continental shelf
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DOI：
10.1002/2014jf003349
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发表时间：
2015-03-01
影响因子：
3.9
通讯作者：
Buffett, B. A.
中科院分区：
文献类型：
--
作者：
Frederick, J. M.;Buffett, B. A.
采用基于有限体积法的二维数值模型，研究了海底地下水排放对近海温、盐度场的影响及其对北美博福特陆架海底多年冻土和天然气水合物现今稳定性的影响。这项研究发现，海底地下水排放对海底多年冻土演化和天然气水合物稳定性有很大影响，这表明局部水文可能像海平面或古气候条件一样强烈地控制海底多年冻土的演化。海底多年冻土演化在潜在的长时间尺度(例如，几个冰川周期)上表现出瞬变行为，然后密度和压力驱动的流动与上覆永久冻土层施加的渗透率变化建立平衡。可探测到的近海多年冻土范围与咸水-淡水过渡的准静态位置有关。更大的海底地下水排泄量允许永久冻土向更远的近海延伸，因为新鲜的孔隙水保存了残留的冰。因此，具有相似古气候历史的地区的永久冻土范围的差异可能部分是由于当地水文的差异。北美博福特陆架上的天然气水合物稳定性可能比目前认为的更普遍，因为低冰饱和度、高度退化的海底永久冻土层可能存在于普通地球物理方法可以检测到的边界之外。
We investigate the role of submarine groundwater discharge on the offshore temperature and salinity field and its effect on the present-day extent of submarine permafrost and gas hydrate stability on the North American Beaufort Shelf with a two-dimensional numerical model based on the finite volume method. This study finds that submarine groundwater discharge can play a large role in submarine permafrost evolution and gas hydrate stability, suggesting that local hydrology may control the evolution of submarine permafrost as strongly as does sea level or paleoclimatic conditions. Submarine permafrost evolution shows transient behavior over potentially long time scales (e.g., several glacial cycles) before a balance of density- and pressure-driven flows is established with the permeability variations imposed by the overlying permafrost layer. The detectable offshore permafrost extent is related to the quasi-stationary location of the saltwater-freshwater transition. Larger values of submarine groundwater discharge allow permafrost to extend farther offshore because fresh pore water preserves relict ice. Therefore, differences in the permafrost extent at locations that share similar paleoclimatic history may be explained in part by differences in the local hydrology. Gas hydrate stability on the North American Beaufort Shelf may be more widespread than currently thought because low-ice saturation, highly degraded submarine permafrost likely exists beyond the boundary detectable by common geophysical methods.