Analysis of the Guiana Abyssal Gyre Experiment [GAGE] Dataset

0241505 麦卡特尼圭亚那深渊环流实验 (GAGE) 在圭亚那盆地放置了一系列系泊的海流计，以测量深边界海流并尝试检测和量化假设的向东流向北流。 实施时，该阵列在 16 N 的条件下放置了 27 个月，GAGE 通过与德国经向翻转变异性实验的合作得到了增强。 （MOVE，总部位于基尔大学）。 GAGE/MOVE 计划总共部署了 10 个系泊点，配有 72 个海流计（测量温度和海流）和 48 个系泊温度/盐度仪器 (CTD)。 在圭亚那盆地结合系泊部署和回收进行了大量的船上 CTD 测量。 GAGE 于 2002 年 5 月完成了现场工作，但有一个 GAGE 系泊装置未能释放，将于 2003 年 3 月恢复。对系泊仪器的初步观察结果证实了冈比亚深渊环流假说。 北纬 16 度处的深西边界流很强，估计为 38 Sverdrups。 在水文学和实测水流中，它具有意想不到的双流态结构：陆上流态在1600 m附近有较强的南流，随深度下降到4000 m附近有弱流，而近海流态在3600-4600 m附近有强流，强度向上减弱，在1600 m处反转为北流。 假设的向北再循环存在于三种状态中。 紧邻近海并毗邻西部深边界流，1600 m 至 5400 m 之间的整个水柱向北流动。 在圭亚那盆地的另一侧，毗邻大西洋中脊，向北的水流从海底 5400 m 延伸至 3600 m。 盆地内 3600 m 及以下的所有阵列仪器，除深边界流中的一台仪器外，均表现出向北流动。 这产生了令人惊讶的强大水流，被称为南极底层水，最冷的深海水。 这些向北流动的要素初步估计为 19-23 Sverdrups，产生 15-19 Sverdrups 的净输送，这是翻转环流冷端的预期幅度。 大型 GAGE/MOVE 数据集将与 MOVE 科学家合作进行处理。 测量的水流和测量的水文学将结合起来，产生 16 N 深度流的完整定量特征，包括其幅度和结构的变化。 以此作为强大的约束，将重新检查圭亚那盆地内的完整水文数据集，以充分描述圭亚那深海环流的特征，并确定其在经向翻转环流冷端中的作用。

0241505 McCartneyThe Guiana Abyssal Gyre Experiment (GAGE) placed a moored array of current meters across the Guiana Basin, to measure the deep boundary current and to attempt to detect and quantify the hypothesized northward flow to its east. As implemented the array was placed at 16 N for 27 months, and GAGE was enhanced through collaboration with a German .Meridional Overturning Variability Experiment. (MOVE, based at U. Kiel). Together the GAGE/MOVE program fielded 10 moorings with 72 current meters (measuring temperatures and currents) and 48 moored temperature/salinity instruments (CTDs). Considerable shipboard CTD measurements were made in the Guiana Basin in concert with mooring deployments and recoveries. GAGE completed its fieldwork in May 2002, with the exception of one GAGE mooring that failed to release and will be recovered in March of 2003. A first look at the results from the moored instruments, confirms the Gambia Abyssal Gyre hypothesis. The deep western boundary current at 16 N is strong, estimated as 38 Sverdrups. It has an unexpected two-regime structure in hydrography and in measured currents: an onshore regime with strong southward flow near 1600 m, declining with depth to weak flow near 4000 m, and an offshore regime with strong flow near 3600-4600 m, declining in strength upwards and reversing to northward flow at 1600 m. The hypothesized northward recirculation is found in three regimes. Immediately offshore and adjacent to the deep western boundary current the entire water column between 1600 m and 5400 m flows northward. On the opposite side of the Guiana Basin adjacent to the Mid-Atlantic Ridge northward flow extends from the seafloor at 5400 m to 3600 m. All array instruments across the Basin at or below 3600 m, except one in the deep boundary current, exhibit northward flow. This yields a surprisingly strong flow of what is called Antarctic Bottom Water, the coldest abyssal water. Together these northward flow elements are preliminarily estimated as 19-23 Sverdrups, yielding a net transport of 15-19 Sverdrups, the expected amplitude for the cold limb of the overturning circulation. The large GAGE/MOVE datasets will be worked up in collaboration with the MOVE scientists. The measured currents and the measured hydrography will be combined to produce a complete quantitative characterization of deep flow at 16 N, including its variabilities in amplitude and structure. With that as a powerful constraint, the full hydrographic dataset within the Guiana Basin will be reexamined to fully characterize the Guiana Abyssal Gyre and establish its role in the cold limb of the meridional overturning circulation.