The Gulf of Maine, a semi-enclosed basin on the continental shelf of the northwest Atlantic Ocean, is fed by surface and deep water flows from outside the Gulf: Scotian Shelf Water from the Nova Scotian shelf that enters the Gulf at the surface, and Slope Water that enters at depth and along the bottom through the Northeast Channel. There are two types of Slope Water, Labrador Slope Water (LSW) and Warm Slope Water (WSW); it is these deep water masses that are the major source of dissolved inorganic nutrients to the Gulf. It has been known for some time that the volume inflow of Slope Waters of either type that enters the Gulf of Maine is variable, that it co-varies with the magnitude of inflowing Scotian Shelf Water, and that periods of greater inflows of Scotian Shelf Water have become more frequent in recent years, accompanied by reduced Slope Water inflows. We present here analyses of a ten-year record of data collected by moored sensors in Jordan Basin, in the interior Gulf of Maine, and in the Northeast Channel, along with recent and historical hydrographic and nutrient data, that help reveal the nature of Scotian Shelf Water and Slope Water inflows. Proportional inflows of nutrient-rich Slope Waters and nutrient-poor Scotian Shelf Waters alternate episodically with one another on time scales of months to several years, creating a variable nutrient field upon which the biological productivities of the Gulf of Maine and Georges Bank depend. Unlike decades past, the inflows of Slope Waters of either type do not appear to be correlated with the North Atlantic Oscillation, which had been shown earlier to influence the relative proportions of the two Slope Waters, WSW and LSW, that enter the Gulf. We suggest that of greater importance in recent years are more frequent, episodic influxes of colder, fresher, less dense, and low-nutrient Scotian Shelf Water into the Gulf of Maine, and concomitant reductions in the inflow of deep, nutrient-rich Slope Waters. We also discuss evidence of modified Gulf Stream ring water that penetrated to Jordan Basin in summer of 2013.

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缅因湾的水团和营养物来源

缅因湾是西北大西洋大陆架上的一个半封闭盆地，由来自海湾外的地表水和深水流供给： 斯科舍陆架 来自新斯科舍陆架的水从地表进入海湾，以及斜坡水通过东北航道沿底部进入深处。坡水有两种类型，拉布拉多坡水（LSW）和暖坡水（WSW）；这些深水团是海湾溶解无机营养物的主要来源。一段时间以来，人们已经知道，进入缅因湾的任一类型的斜坡水域的流入量是可变的，它与流入斯科舍陆架水的大小共同变化，并且斯科舍陆架水流入量较大的时期近年来，这种情况变得更加频繁，同时斜坡水流入量也减少了。我们在此分析了约旦盆地、缅因州内湾和东北海峡的系泊传感器收集的十年数据记录，以及最近和历史的水文和营养数据，这些数据有助于揭示斯科舍省的性质陆架水和斜坡水流入。营养丰富的斜坡水域和营养贫乏的斯科舍陆架水域的比例流入在数月至数年的时间尺度上间歇性地交替，形成了缅因湾和乔治浅滩的生物生产力所依赖的可变营养场。与过去几十年不同，这两种类型的斜坡水域的流入量似乎都与北大西洋涛动无关，而北大西洋涛动早前已被证明会影响进入海湾的两种斜坡水域（WSW 和 LSW）的相对比例。我们认为，近年来更重要的是更冷、更新鲜、密度较小和低营养的斯科舍陆架水更频繁地、间歇性地流入缅因湾，以及随之而来的深层、营养丰富的斜坡水域的流入量减少。我们还讨论了 2013 年夏季墨西哥湾流环流水渗入约旦盆地的证据。