The accurate digitization of historical sea level records

IF 3.3 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
Patrick J. McLoughlin, Gerard D. McCarthy, Glenn Nolan, Rosemarie Lawlor, Kieran Hickey
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Abstract

Understanding regional sea level variations is crucial for assessing coastal vulnerability, with accurate sea level data playing a pivotal role. Utilizing historical sea level marigrams can enhance datasets, but current digitization techniques face challenges such as bends and skews in paper charts, impacting sea level values. This study explores often-overlooked issues during marigram digitization, focusing on the case study of Dún Laoghaire in Ireland (1925–1931). The methodology involves digitizing the original marigram trace and underlying grid to assess offsets at the nearest ft (foot) interval on the paper chart, corresponding to changes in the water level trace for each hour interval. Subtracting the digitized value from the known value (the actual measurement) allows for the determination of differences, which are then subtracted from each hourly trace value. After adjusting for offsets ranging from −3.962 to 13.716 mm (millimetres), the study improves the final accuracy of sea level data to approximately the 10 mm level. Notably, data from 1926 and 1931 exhibit modest offsets (<7 mm), while other years show more substantial offsets (>9–14 mm), emphasizing the importance of adjustments for accuracy. Such 10 mm accuracy is compatible with requirements of the Global Sea Level Observing System. Comparing the adjusted digitized data with other survey data shows similar amplitudes and phases for Dún Laoghaire in both the historical and modern datasets, and there is an overall mean sea level rise of 1.5 mm/year when combined with the available data from the Dublin region.

Abstract Image

历史海平面记录的精确数字化
了解区域海平面变化对于评估沿海地区的脆弱性至关重要,而准确的海平面数据则起着关键作用。利用历史海平面海图可以增强数据集,但目前的数字化技术面临着一些挑战,如纸质海图的弯曲和倾斜会影响海平面数值。本研究以爱尔兰邓莱里海图(1925-1931 年)为案例,探讨了海图数字化过程中经常被忽视的问题。该方法包括对原始海图轨迹和基础网格进行数字化,以评估纸质海图上最近英尺(呎)间隔的偏移量,这些偏移量与每小时间隔的水位轨迹变化相对应。将数字化值从已知值(实际测量值)中减去,即可确定差值,然后再从每小时的水位跟踪值中减去差值。在对-3.962 至 13.716 毫米(毫米)的偏移量进行调整后,这项研究将海平面数据的最终精确度提高到大约 10 毫米的水平。值得注意的是,1926 年和 1931 年的数据显示出适度偏移(7 毫米),而其他年份的数据则显示出更大的偏移(9-14 毫米),这强调了调整精度的重要性。10 毫米的精度符合全球海平面观测系统的要求。将调整后的数字化数据与其他勘测数据进行比较后发现,无论是历史数据还是现代数据集,邓莱里的振幅和相位都很相似,结合都柏林地区的现有数据,总体平均海平面上升幅度为 1.5 毫米/年。
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来源期刊
Geoscience Data Journal
Geoscience Data Journal GEOSCIENCES, MULTIDISCIPLINARYMETEOROLOGY-METEOROLOGY & ATMOSPHERIC SCIENCES
CiteScore
5.90
自引率
9.40%
发文量
35
审稿时长
4 weeks
期刊介绍: Geoscience Data Journal provides an Open Access platform where scientific data can be formally published, in a way that includes scientific peer-review. Thus the dataset creator attains full credit for their efforts, while also improving the scientific record, providing version control for the community and allowing major datasets to be fully described, cited and discovered. An online-only journal, GDJ publishes short data papers cross-linked to – and citing – datasets that have been deposited in approved data centres and awarded DOIs. The journal will also accept articles on data services, and articles which support and inform data publishing best practices. Data is at the heart of science and scientific endeavour. The curation of data and the science associated with it is as important as ever in our understanding of the changing earth system and thereby enabling us to make future predictions. Geoscience Data Journal is working with recognised Data Centres across the globe to develop the future strategy for data publication, the recognition of the value of data and the communication and exploitation of data to the wider science and stakeholder communities.
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