Regime Shift in the Gulf of Maine
Regime Shift in the Gulf of Maine
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缅因湾的政权更迭
DOI：
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发表时间：
2015
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影响因子：
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通讯作者：
Smith
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文献类型：
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作者：
Peter;C.;Smith
-基于25年（1975-2000）的观察，传统观点认为缅因湾（GoM）的流入主要发生在两个区域：新斯科舍省塞布尔角附近的斯科舍大陆架近海和东北海峡（NEC）的东侧。特别是，东北海东的月平均海流在所有季节和所有深度都显示出持续的流入，除了在底部（~200米）附近偶尔但短暂的反转。相反，NEC西侧的水流通常在表层和中深方向流出海湾，与乔治海岸上的顺时针环流一致，但这些水流在较深层（150-200米）确实表现出相对频繁的流入反转，与东侧的水流一致。在2000年的某个时候，当最后一个贝德福德海洋研究所(BIO)/美国GLOBEC系泊从NEC东部移除，2004年，当一个新的系泊被放置在那里作为美国海洋观测阵列的一部分时，发生了转变。最近从东日本东北地区一个代表性地点收集的数据显示了强烈的季节性水流信号，其特征是在深层（bbb - 100米）持续流出，特别是在冬季。Pettigrew等人（2008）首次报道了这一观察结果，其中流出流偶尔也会延伸到表层，最明显的是在2004-2005年和2006-2007年的冬季。本文报道的其他数据和分析表明，NEC洋流中的这种新行为模式可能对墨西哥湾生态系统产生重要影响。本文还讨论了NEC环流中这种“状态转移”的可能原因，以及对墨西哥湾深水营养场和生态系统的影响。*通讯作者：peter.smith@dfo-mpo.gc.ca
—Conventional wisdom, based on observations spanning two and a half decades (1975–2000), asserts that inflow to the Gulf of Maine (GoM) occurs primarily in two areas: inshore on the Scotian Shelf off Cape Sable, Nova Scotia and on the eastern side of the Northeast Channel (NEC). In particular, the monthly mean currents in the eastern NEC have shown persistent inflow at all depths and in all seasons, except for the occasional, but brief, reversals near the bottom (~200 m). Conversely, the flow on the western side of the NEC is normally directed out of the gulf in the surface layer and at mid-depth, consistent with the clockwise gyre over Georges Bank, but those currents do show relatively frequent reversals to inflow in the deeper layers (150–200 m), in sympathy with the flow on the eastern side. At some point between the year 2000, when the last Bedford Institute of Oceanography (BIO)/U.S. GLOBEC mooring was removed from the eastern NEC, and 2004, when a new mooring was placed there as part of the U.S. ocean observing array, a transformation occurred. The recent data, collected from a representative location in the eastern NEC, show a strongly seasonal current signal marked by persistent periods of outflow in the deep layers (>100 m), particularly in winter. This observation was first reported by Pettigrew et al. (2008), where the outflow currents occasionally extend to the surface layers as well, most notably in the winters of 2004–2005 and 2006–2007. Additional data and analyses reported here suggest that this new mode of behavior in the NEC currents could have important consequences for the GoM ecosystem. Possible causes for this “regime shift” in the NEC circulation and implications for the GoM deepwater nutrient fields and ecosystem are discussed. * Corresponding author: peter.smith@dfo-mpo.gc.ca