Time-Series of Cloud-Free Sentinel-2 NDVI Data Used in Mapping the Onset of Growth of Central Spitsbergen, Svalbard

• Published in: Remote sensing (Basel, Switzerland) Vol. 13; no. 15; p. 3031
• Main Authors: Karlsen, Stein Rune, Stendardi, Laura, Tømmervik, Hans, Nilsen, Lennart, Arntzen, Ingar, Cooper, Elisabeth J.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.08.2021; MDPI
• Subjects: Bioindicators; Cameras; Climate change; Cloud cover; Datasets; Flowers & plants; Ground-based observation; Ice; Indicator species; Mapping; Matematikk og Naturvitenskap: 400; Mathematics and natural science: 400; NDVI; onset of growth; Phenology; Productivity; Remote sensing; Sentinel-2; Svalbard; Taiga & tundra; Time series; Tundra; VDP; Vegetation; Spitsbergen Island; Norway; Svalbard Islands; Arctic region
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs13153031

The Arctic is a region that is expected to experience a high increase in temperature. Changes in the timing of phenological phases, such as the onset of growth (as observed by remote sensing), is a sensitive bio-indicator of climate change. In this paper, the study area was the central part of Spitsbergen, Svalbard, located between 77.28°N and 78.44°N. The goals of this study were: (1) to prepare, analyze and present a cloud-free time-series of daily Sentinel-2 NDVI datasets for the 2016 to 2019 seasons, and (2) to demonstrate the use of the dataset in mapping the onset of growth. Due to a short and intense period with greening-up and frequent cloud cover, all the cloud-free Sentinel-2 data were used. The onset of growth was then mapped by a NDVI threshold method, which showed significant correlation (r2 = 0.47, n = 38, p < 0.0001) with ground-based phenocam observation of the onset of growth in seven vegetation types. However, large bias was found between the Sentinel-2 NDVI-based mapped onset of growth and the phenocam-based onset of growth in a moss tundra, which indicates that the data in these vegetation types must be interpreted with care. In 2018, the onset of growth was about 10 days earlier compared to 2017.