以超導及衛星重力決定黑潮時變：氣候變遷對海洋環流及海水位的影響

Abstract

超導重力儀，以及其他數種高科技大地測量技術，包含重力觀測與海洋測高衛星的資料，將被用來研究黑潮，以及上游的海洋力學研究區(KUDEX)。其中自2006年設立在新竹重力基準站的超導重力儀，能夠以1 Hz的取樣頻率搜集重力觀測。超導重力儀所提供的重力觀測時間序列，包含相當寬廣的頻率，其週期從數小時到數年不等。這些訊號可與測站周遭數公里，或是半個地球外的質量變遷，以牛頓萬有引力的方式，或是地球彈性負載相關聯。另一方面，重力觀測衛星，例如GRACE，具有幾乎完整的空間涵蓋能力足以包含地球表面。在這個研究當中，將嘗試發展其線區域解的技術，將原本全球性的重力場解集中在指定的區域，如此能為這個主題，西太平洋黑潮相關區域的重力異常空間解析度提升到頂點，尤其是針對台灣附近。超導重力觀測與衛星重力觀測資料所關連的是質量變遷的監測，同時，衛星測高所得的海水面則與體積變化有所關聯。所以，這些大地測量資料的結合第一種功能是用來與海洋動力模式的預估進行比對驗證。另一種功能則是藉由兩類資料的交互分析，可以研究海水的熱膨脹效應。由於此主題中所涉及的黑潮訊號與環境噪訊比較起來相對微弱。所以發展這些環境因子的最佳模式，並用之與觀測數據改正是非常重要的。這個研究，預期將可以為海洋科學的研究，帶來一種嶄新的發法。

The superconducting gravimeter, along with several cutting edge geodetic techniques including the gravity recovery satellite and altimeters will be dedicated into the study of Kuroshio Current, as well as the KUDEX (Kuroshio Upstream Dynamics EXperiment) area. The superconducting gravimeter, which has been installed at Hsinchu gravimetry observatory since 2006, is able to collect gravity data at 1 Hz sampling rate. The gravity data series output by a superconducting gravimeter has a broad band spectrum covering all sorts of signals with period from hours to inter-annual band; those signals may associate with mass re-distribution from a distance of several kilometers to a hemisphere away through either the observed Newtonian attraction force or elastic loading. On the other hand, the gravity recovery satellite mission, GRACE, has a more or less comprehensive spatial coverage of the Earth. This study plans to enhance the global resolution of GRACE by regional solution so that satellite observation may find its focus on west Pacific, particularly the vicinity around Taiwan. The gravimetrical data derived from the superconducting gravimeter and the gravity recovery satellite together serve as the monitoring of oceanic mass re-distribution. In the mean time, the sea level monitoring by satellite altimeters tracks the sea water variation in the sense of volumetric change. The first purpose to carry out the fusion of these geodetic data sets is to serve the validation for the oceanographic models. Secondly, the cross-analysis of these geodetic data sets, including the mass re-distribution and the volumetric variation, can be applied to study the thermo steric sea level change. Since the expected signals induced by oceanic current are relatively weak compared with noise from environmental factors, state of the art techniques are essential for modeling and correction. The development of modeling approaches in this regard is an important issue to identify signal from Kuroshio. It is expected that this proposed study should pioneer a new methodology to investigate oceanography.