Collaborative Research: Ocean Pressure in the Arctic Derived From Satellite Gravity Observations and In Situ Pressure Measurements

该研究将利用深海压力、水文和大气数据以及卫星重力的现场观测，估计北冰洋底部压力、海平面和环流的大尺度季节性和较长时间变化。北冰洋中部的海平面是海洋环流的关键决定因素，因此它强烈影响海冰分布和区域淡水收支。气候变率与与海冰分布变化相关的反照率变化以及与北冰洋淡水和海冰输出变化相关的全球温盐环流变化有关。因此，观察海洋中的压力分布对于理解海洋环流的可变性至关重要。目前对冰和淡水分布及其变化的看法是基于现有的水文调查和一些自动化仪器的测量。由于缺乏常规的、空间上连续的淡水分布测量，因此很难在任何时候绘制出锋面位置的完整图像。这项工作的科学目标和优点是改进与气候变率有关的海洋变化指数，并有助于实现从空间获得大尺度海洋环流和淡水分布的系统测量的目标。海底压力记录仪（bpr）将部署在一个100公里长的三角形阵列中，其顶点位于北极、罗蒙诺索夫海岭和靠近海岭脚下的地方。这些现场测量结果将与GRACE（重力恢复和气候实验卫星任务）对北冰洋中部深海底部压力的估计进行比较，以交叉验证这些压力恢复方法。BPRs还提供潮汐和其他短期（60天）变化的测量，并将用于减少卫星测量中的混叠问题。整个盆地的GRACE随时间变化的底压场将与实测底压、沿海海平面记录和水文数据进行比较，以估计海洋环流变化，从而评估遥感和原位测量相结合方法的准确性。这项工作将有助于实现将遥感测得的海底压力与卫星高度计测得的海面高度进行比较的长期目标，不仅可以估算环流变化，还可以估算总空间异常以及推断的淡水和海冰含量。本工作的结果包括原位BPR记录、导出的潮汐成分、漂移校正、去除潮汐后的漂移校正压力，以及去除潮汐后GRACE估计的底压空间场。这些数据将被存档在ARCSS和SEARCH数据库中，并直接提供给北冰洋海平面观测系统的合作者。为了更广泛的传播，压力衍生的海平面梯度和正压输送估计将在网络上提供，并存档在ARCSS和SEARCH数据库中。该项目将建立三个机构之间的合作：华盛顿大学和科罗拉多大学以及喷气推进实验室，并将需要几个学科的专业知识：海洋学、大地测量学和固体地球物理学。这项工作将成为华盛顿大学一名研究生的博士论文项目和科罗拉多大学一名研究生博士项目的一部分，将是将时变卫星重力观测纳入物理海洋学的第一步。这些观测为海洋学提供了一种新的和创新的数据类型，对改善和更广泛地了解极地和全球海洋环流具有很大的希望。

The research will estimate the large-scale seasonal and longer time variations in the Arctic Ocean bottom pressure, sea level, and circulation using in-situ observations of deep- sea pressure, hydrographic and atmospheric data, and satellite gravity. Sea level in the central Arctic Ocean is a crucial determinant of the ocean's circulation, and as such it strongly affects the sea-ice distribution and the regional freshwater budget. Climate variability is linked to changes in albedo associated with changes in sea-ice distribution and to changes in the global thermohaline circulation associated with changes in the export of Arctic Ocean freshwater and sea ice. Observing the pressure distribution in the ocean is thus central to understanding the variability in the ocean circulation. Current perspectives of the ice and freshwater distribution and their variations are based on available hydrographic surveys and measurements from a few automated instruments. The lack of routine, spatially continuous measurements of the freshwater distribution makes it difficult to construct a complete picture of frontal locations at any one time. The scientific goal and merit of this work is to improve indices of ocean change related to climate variability and to contribute to achieving the goal of obtaining systematic measurements of large-scale ocean circulation and freshwater distribution from space. Bottom pressure recorders (BPRs) will be deployed in a 100 km triangular array with vertices at the Pole, the Lomonosov Ridge, and near the foot of the ridge. These in situ measurements will be compared with GRACE (the Gravity Recovery and Climate Experiment satellite mission) estimates of deep-sea bottom pressure in the central Arctic Ocean to cross- validate these methods of pressure retrieval. BPRs also provide measurements of tides and other short period ( 60 days) variability, and will be used to reduce aliasing problems in the satellite measurements. GRACE time-dependent bottom pressure fields for the whole basin will be compared with measured bottom pressure, coastal sea level records, and hydrographic data to estimate ocean circulation changes and thereby evaluate the accuracy of the combined remote sensing, in situ measurement approach. This work will contribute to the long-term goal of comparing remote sensing measurements of bottom pressure with satellite altimeter observations of sea surface height to produce not only estimates of circulation changes but also estimates of the total steric anomaly and inferred fresh water and sea ice content. Results from this work include in situ BPR records, derived tidal constituents, drift corrections, the drift corrected pressure with tides removed, and the spatial field of bottom pressure estimates from GRACE after tide removal. These will be archived in the ARCSS and SEARCH data banks and supplied directly to those collaborating on the system of Arctic Ocean sea-level observations. For broader dissemination, pressure-derived sea-level gradient and barotropic transport estimates will made available on the Web as well as archived in the ARCSS and SEARCH data banks. This project will establish collaborations between three institutions: the Universities of Washington and Colorado, and the Jet Propulsion Laboratory, and will require expertise in several disciplines: oceanography, geodesy, and solid earth geophysics. The work, which will form the PhD thesis project of a University of Washington graduate student and part of the PhD project of a University of Colorado graduate student, will be a first step towards integrating time-variable satellite gravity observations into physical oceanography. These observations constitute a new and innovative data type for oceanography, with considerable promise for improved and broader understanding of the circulation of the polar and global oceans.