国际Argo计划执行现状剖析

国际Argo计划自2000年实施以来,世界上25个国家和团体已经在全球海洋中布放了5000余个Argo浮标,其中在海上正常工作的浮标已经超过3000个。这标志着全球Argo实时海洋观测网已经全面建成。文中将系统介绍国际Argo计划主要成员国在浮标布放、回收和Argo资料管理等方面所作出的贡献,以帮助读者对这21世纪的重大国际海洋观测计划有一较全面、深入的了解。     

应用Argo资料分析西北太平洋冬、夏季水团

应用Argo剖面浮标观测的温、盐度资料,分析了西北太平洋海域冬、夏季的温、盐度分布、水团结构及其分布。首先采用T-S点聚图法分析了该海域水团分布的基本情况,由点聚分析结果可知,该海域至少存在6种以上水团;再用模糊聚类软化法对水团作进一步划分,分别计算了该海域6至11类水团的F和△F值,结果表明,冬、夏季的△F值都以划分为8类时为最大,这与大洋水团的稳定性是一致的,因此,该海域冬、夏季水团以划分为8类最佳,它们分别是北太平洋热带表层水、北太平洋次表层水、北太平洋中层水、北太平洋副热带模态水、北太平洋深层水和赤道表层水,以及南太平洋次表层水和南太平洋中层水。     

一种针对侧扫声纳图像的数字镶嵌技术方法

以南海某海域实测侧扫声纳数据为例,研究侧扫声纳图像的数字镶嵌技术方法,对关键步骤进行详细的阐述。通过对原始侧扫声纳数据进行导航数据校正、海底线跟踪、斜距改正、TVG校正、船速校正、地理编码与重采样、拼接与镶嵌等处理,生成大区域、大范围、高分辨率、无缝拼接的侧扫声纳图像。实验结果证明声纳图像数字镶嵌技术的有效性,并取得理想的效果。     

Flow processes and sediment deformation in the Canary Debris Flow on the NW African Continental Rise

The Canary Debris Flow formed an extensive deposit on the NW African Continental Margin west of the Canary Islands. Sidescan sonar images and 3.5-kHz profiles show that the middle part of the debris flow deposit consists of complex channel systems separated by banks and ridges of debris. Channels are typically up to 10 km wide and 10 to 20 m deep, and have little or no debris fill. They appear to feed a more laterally continuous debris flow sheet which is seen further downslope. Interchannel banks and ridges are composed of 5 to 20 m thick debris deposits. This morphology is remarkably similar to that seen in subaerial debris flows, and we therefore infer that the observed submarine debris flow morphology is a primary flow fabric, rather than the result of the debris flow interacting with or exploiting pre-existing channels. High-resolution Sidescan sonar images show that the debris flow surface is covered by sediment blocks up to 300 m in diameter. A single core collected from the flow shows that most of the 4.6-m flow thickness at the core site is composed of a single clast. The clast has been folded, with its upper part consisting of an inverted minor image of the lower part. The same sequence occurs again, in situ, beneath the debris flow, suggesting that the clast may have a local source, rather than having been derived from the debris flow source area, some 200 km upslope. This indicates that the debris flow was capable of substantial seabed erosion in the middle part of its course. In these middle reaches, erosion within the channelled areas probably occurred simultaneously with deposition in the interchannel areas. Interchannel deposits may contain both locally derived and original source area material.     

Bathymetric mapping and sub-bottom profiling through lake ice with ground-penetrating radar

Bathymetric mapping of lakes with sonar is essentially limited to the ice-free summer months. Recent developments in ground-penetrating radar technology have greatly increased its portability and capabilities for imaging through fresh water. The suitability of a backpack portable ground-penetrating radar (GPR) system for bathymetric mapping of ice-covered Arctic lakes was investigated by performing grid surveys on three lakes with water depths up to 19 m. It was demonstrated that GPR can now be used to quickly produce high quality bathymetric maps and sub-bottom profiles showing sediment type and lacustrine sediment thickness. While water depths were measured with a precision of ±3%, lacustrine sediment thickness measurements (up to 5 m) had an estimated precision of ±15%.     

侧扫声呐图像分割的中性集合与量子粒子群算法

针对现有的侧扫声呐图像分割方法存在分割准确率不高和效率偏低的问题,提出了一种基于中性集合和量子粒子群算法的侧扫声呐图像阈值分割方法。通过基于中性集合计算图像灰度共生矩阵,实现了侧扫声呐图像精细纹理的表达,提高了分割精度;基于二维最大熵理论,采用量子粒子群算法计算二维最优分割阈值向量,实现了分割阈值向量的快速准确获取,提高了分割效率和精度。最终实现了高噪声侧扫声呐图像目标的准确、高效分割。通过对含有不同目标的侧扫声呐图像的分割试验,验证了该算法的有效性。     

Strike-slip tectonic processes in the northern Caribbean between Cuba and Hispaniola (Windward Passage)

Marine geophysical data including Seabeam, seismic reflection, magnetics, gravimetry and side-scan sonar have been recently collected along the northern Caribbean strike-slip plate boundary between Cuba and Hispaniola, in the Windward Passage area. The analysis of this comprehensive data set allows us to illustrate active strike-slip tectonic processes in relation to the kinematics of the Caribbean Plate. We show that the transcurrent plate boundary trace runs straight across the Windward Passage, from the southern Cuban Margin in the west (Oriente Fault) to the Tortue Channel in the east. The Windward Passage Deep is thus not an active pull-apart basin, as previously suggested. The plate boundary geometry implies that the motion of the Caribbean Plate relative to the North American Plate is partitioned between a strike-slip component, accommodated by the Windward Passage active fault zone, and a convergence component, accommodated by compression at the bottom of the Northern Hispaniola Margin. On the basis of a correlation with onland geological data, an age is given to the stratigraphic sequences identified on seismic profiles. A kinematic reconstruction is proposed that follows the tectonic unconformities recognized at sea and on land (Late Eocene, Early Miocene, Middle Miocene and Late Pliocene). Each one of these tectonic events corresponds to a drastic reorganization of the plate boundary geometry. We propose to correlate these events with successive collisions of the northern Caribbean mobile terranes against the Bahamas Bank. During each event, the plate boundary trace is shifted to the south and a part of the Caribbean Plate is accreted to North America.