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首页> 外文期刊>Continental Shelf Research: A Companion Journal to Deep-Sea Research and Progress in Oceanography >Temporal and spatial variability of ADCP backscatter on a continental slope
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Temporal and spatial variability of ADCP backscatter on a continental slope

机译：大陆坡ADCP背向散射的时空变化

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Previous research has shown that acoustic volume backscatter intensity (ABI) from an acoustic Doppler current profiler (ADCP) can be a proxy for zooplankton and micronekton biomass over time or space. As part of NOAA's Sperm Whale and Acoustic Monitoring Program (SWAMP) and a follow-on ichthyoplankton survey (SEAMAP), a ship-mounted 300-kHz broadband ADCP collected current velocity and ABI data from July to September 2001 in the northeast Gulf of Mexico. The present study sought to compare/contrast the variability in ABI both spatially and temporally using the data obtained from the SWAMP and SEAMAP cruises. The ADCP data were averaged over 2 min and 4 m vertical bins from 16 to 56 m below sea surface. Usually, ABI in this epipelagic realm averaged 3 dB higher at night than during the day because of diet vertical migration of zooplankton and micronekton into these near surface waters, while in a region having cyclonic circulation along the continental margin of the northeast Gulf, ABI averaged 6 dB higher than in an anticyclonic warm filament there. Wet displacement volumes (WDV) were measured using Bongo net tows to estimate that a 6 dB increase in ABI was equivalent to an increase from 9 to 10.5 ml WDV of plankton + micronekton per 100 m(3). Sperm whale abundance has been shown to be positively correlated with regions of locally high ABI, and sperm whale sightings during SWAMP were also compared to our ABI measurements. Spectral and Empirical Orthogonal Function analyses were performed on subsets of the ABI data for which 10-14 day time series were available and showed 2-3 day periodicity near-surface, corresponding to spatial scales of 10(1)-10(2) km. During summer 2001, the mesoscale circulation along the subtropical continental margin in the northeastern Gulf was found to be the principal forcing factor for low frequency ABI variation. Increased backscatter observations are also correlated with offshore flow from the continental margin to the deep ocean, particularly when the offshore flow is close to a river delta. (C) 2004 Elsevier Ltd. All rights reserved.
机译：先前的研究表明，来自声多普勒电流剖面仪（ADCP）的声体积反向散射强度（ABI）可以替代浮游动物和微浮游生物在时间或空间上的生物量。作为NOAA的抹香鲸和声学监测计划（SWAMP）和后续的浮游鱼类调查（SEAMAP）的一部分，一艘船载300 kHz宽带ADCP收集了墨西哥东北部2001年7月至2001年9月的当前速度和ABI数据。本研究试图使用从SWAMP和SEAMAP巡航获得的数据来比较/对比ABI在空间和时间上的变异性。 ADCP数据是在2分钟和海平面以下16至56 m的4 m垂直箱中平均的。通常，由于浮游动物和微动物的饮食在垂直方向上向这些近地表水的垂直迁移，该上流域的ABI在夜间平均要比白天高3 dB，而在东北海湾大陆边缘沿气旋环流的地区，ABI的平均值比那里的抗气旋暖丝高6 dB。使用Bongo净丝束测量湿排量（WDV），以估计ABI每增加6 dB，ABI就从每100 m浮游生物+微浮游生物从9 ml的WDV增加到10.5 ml（3）。抹香鲸的丰度已被证明与当地较高的ABI呈正相关，并且还将SWAMP期间发现的抹香鲸与我们的ABI测量值进行了比较。对可获得10-14天时间序列的ABI数据子集进行了光谱和经验正交函数分析，并显示了近地表2-3天的周期性，对应于10（1）-10（2）km的空间尺度。在2001年夏季，发现东北海湾亚热带大陆边缘的中尺度环流是低频ABI变化的主要推动因素。背向散射观测值的增加也与从大陆边缘到深海的近海流量相关，特别是当近海流量接近河流三角洲时。 （C）2004 Elsevier Ltd.保留所有权利。

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