AON: Sustained observation and analysis of the Arctic upper ocean thermohaline stratification

北极正在迅速变化。季节性冰融化的开始在一年中发生得更早，而秋季冻结的日期也更晚。海冰覆盖的横向范围、厚度和年龄都急剧减少。观测到地表水显著变新鲜，同时几个次表层也在变暖。额外的海洋热量导致额外的海冰融化。所有这些变化都对极地生态系统、地球气候状态和近岸土著社区的恢复能力产生了影响，也对人类对北纬高纬度地区的利用产生了影响，包括商业航运、自然资源开采、生态旅游以及随之而来的搜索、救援和防御活动。从历史上看，被冰雪覆盖的北冰洋很少被观测到，尤其是在冬季。伍兹霍尔海洋研究所（Woods Hole Oceanographic Institution）于2003- 2004年开发的冰系剖面仪（ITP），旨在对北冰洋上游的水特性和海冰在所有季节的运动进行采样，并将这些数据实时传输给岸上用户。该系统由一个表面浮标组成，浮标通常部署在浮冰上，支撑着一根穿过冰层延伸到800米深的钢丝绳系绳，以及一个水下航行器，它可以反复地在系绳上上下爬行，携带传感器，对海水的温度和盐度等特性进行采样。迄今为止，已经在北极部署了大约100个ITP系统（每个系统运行1-3年），这些系统总共返回了超过70,000次北冰洋水特性观测以及近150年的冰漂数据，所有这些都为美国国家科学基金会的北极观测网络计划做出了贡献。这些数据已被世界各地的研究人员和学生以及业务机构使用（到目前为止，已经发表了大约150篇同行评议论文，这些论文直接利用了ITP数据，引用了基于ITP观察的研究或以其他方式引用了ITP计划）。目前的研究项目将在5年内继续开展这项活动，因为持续的观测被认为对记录和了解北极目前正在发生的快速变化并预测其未来演变至关重要。计划进行三管齐下的工作，包括：1)每年部署常规的ITP； 2)开发、测试和部署一种新仪器，即专注于水柱上部100 - 200米的系绳海洋剖面仪（TOP）； 3)对生成的ITP和TOP数据进行科学分析。后者的最初重点将是北极地表水及其与海冰的相互作用。与过去一样，来自这些自主仪器的数据将通过项目网站、全球电信系统网络、北极数据中心和国家环境信息中心公开发布。除了科学和工程，这个新项目还将加强ITP网站，并为WHOI展览中心开发一个展示，让公众更广泛地了解目前正在进行的研究和令人兴奋的工程，以及在这一剧烈变化时期收集北极信息的原因。从技术上讲，新合同将支持WHOI冰系绳剖面仪项目的延续，其范围和活动与近年来类似。在项目的前4年中，每年将建立并部署4个标准的ITP系统，具有实时数据恢复、自动化处理和分发功能。来自每个ITP系统的实时数据将包括每日（或更频繁）2米分辨率的海洋温度和盐度垂直剖面图（以及原始数据）和每小时或更精确的浮标位置固定，由此可以推导出冰速。此外，与过去一样，恢复的数据将被编辑、校准和网格化，这些科学质量的产品一旦完成就会向公众开放。新的Tethered Ocean Profiler开发活动每年将贡献2个可操作的TOP系统。TOP数据处理和分发将与ITP协议并行。ITP和TOP浮标的部署将每年根据可用的考察来决定，其目标是（与其他浮标计划合作）维持北极深处的广泛空间覆盖。除了继续目前的数据处理之外，新项目将创建和维护一个按位置和时间归档的ITP个人档案数据库，并开发和支持一个实用工具工具箱，以方便学生/博士后、同行科学家和精通计算机的普通公众对这些观察结果进行探索和分析。设想的数据库将保存netCDF格式的个人配置文件数据，以及用Matlab和Python编写的函数，以提取并按指定向用户呈现数据子集。档案将可从ITP计划网站访问，并提供给国家数据中心存档。研究的最初科学主题将集中在北冰洋表面混合层，使用来自ITPs和载人站的组合数据集来记录北极地理子域的混合层厚度（使用各种标准）、温度和盐度随时间的变化。反过来，这些特征（以及任何随时间变化的趋势）将通过直接相关和简单模式相对于地表强迫（海气热和动量交换、海冰增长和融化）进行评估。重点将从2000年到现在。项目首席调查员和其他人员对这些新观测结果的分析将有助于更好地了解北冰洋发生的极端变化及其对地球气候、极地生态系统和极北地区人类活动的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Arctic is changing rapidly. Onset of seasonal ice melt is occurring earlier in the year with a later date of fall freeze up. There has been a dramatic reduction in the lateral extent, thickness and age of the sea ice cover. Significant freshening of surface waters has been observed along with warming in several subsurface layers. Additional ocean heat contributes to additional sea ice melting. All of these changes have consequences for the polar ecosystem, earth's climate state and the resilience of near-shore native communities, as well as impact on human use of the high northern latitudes including commercial shipping, natural resource extraction, ecotourism and the accompanying search, rescue and defense activities. Historically, the ice-covered Arctic Ocean has been poorly observed, particularly in winter. The Ice-Tethered Profiler instrument (ITP), developed at the Woods Hole Oceanographic Institution in 2003-4, is designed to sample the upper Arctic Ocean water properties and sea ice motion in all seasons and transmit those data to shore-side users in real time. The system consists of a surface buoy typically deployed on an ice floe that supports a wire rope tether extending through the ice down to around 800 m depth, and an underwater vehicle that repeatedly crawls up and down the tether carrying sensors that sample sea water properties such as temperature and salinity. To date, approximately 100 ITP systems have been deployed in the Arctic (each operating for 1-3 years) that have collectively returned more than 70,000 observations of Arctic Ocean water properties as well as nearly 150 cumulative years of ice drift data, all contributing to the National Science Foundation's Arctic Observing Network program. These data have been used by researchers and students (so far resulting in approximately 150 published peer-reviewed papers that have directly utilized ITP data, cited research based on ITP observations or otherwise referenced the ITP program) as well as operational agencies the world over. The present research project will continue this activity for a 5-year period as sustained observations are considered vital to documenting and understanding the rapid changes now underway in the Arctic and predicting its future evolution. A three-pronged effort is planned that consists of 1) annual deployment of conventional ITPs, 2) development, testing and then operational deployments of a new instrument, the Tethered Ocean Profiler (TOP) that focuses on the upper 100 200 m of the water column, and 3) scientific analysis of the resulting ITP and TOP data. Initial focus of the latter will be the Arctic surface waters and their interaction with the sea ice. As in the past, data from these autonomous instruments will be publicly distributed via the project website, the Global Telecommunications System network, the Arctic Data Center and the National Center for Environmental Information. Beyond science and engineering, the new project will enhance the ITP website and develop a display for the WHOI Exhibition Center to provide the public with a broader understanding of the research and the exciting engineering now underway, along with the reasons to gather Arctic information during this time of dramatic change.Technically, the new award will support continuation of the WHOI Ice-Tethered Profiler project with similar scope and activity as in recent years. Four standard ITP systems will be built and fielded in each of the first 4 years of the project with real time data recovery, automated processing and distribution. The real-time data from each ITP system will consist of daily (or more frequent) vertical profiles of ocean temperature and salinity at 2-m resolution (as well as the raw data) and hourly or better buoy position fixes from which ice velocity may be derived. Also, as in the past, the recovered data will be edited, calibrated and gridded, with these science-quality products being made publicly available as soon as they are completed. The new Tethered Ocean Profiler development activity will contribute 2 operational TOP systems annually. TOP data handling and distribution will parallel the ITP protocol. Deployments of ITP and TOP buoys will be decided annually in light of available expeditions with the goal (in collaboration with other buoy programs) of sustaining broad spatial coverage of the deep Arctic. Beyond continuing the present data handling, the new project will create and maintain a data base of individual ITP profiles archived by position and time, and develop and support a utilities toolbox to facilitate exploration and analysis of these observations by students/postdocs, fellow scientists, and computer-savvy members of the general public. The envisioned data base will hold individual profile data in netCDF format together with functions written in both Matlab and Python to extract and present data subsets to the user as specified. The archive will be accessible from the ITP program website as well as offered to the national data centers for archival. The initial science topic that will be investigated will focus on the Arctic Ocean surface mixed layer, using a combined dataset from ITPs and manned stations to document mixed layer thickness (using a variety of criteria), temperature and salinity in Arctic geographic subdomains versus time. In turn, these characteristics (and any trends with time) will be assessed relative to surface forcing (air-sea exchange of heat and momentum, sea ice growth and melt) through direct correlation and simple models. Focus will be the period from 2000 to present. Analysis of these new observations by the project Principal Investigators and others will contribute to a better understanding of the extreme changes taking place in the Arctic Ocean and their impacts on earth's climate, the polar ecosystem and human activities in the far north.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.