Recent Changes of Phytoplankton Bloom Phenology in the Northern High‐Latitude Oceans (2003–2020). Issue 10 (25th October 2022)

• Record Type: Journal Article
• Authors: Zhao, Haipeng; Matsuoka, Atsushi; Manizza, Manfredi; Winter, Amos
• Is Part Of: Journal of geophysical research. Volume 127:Issue 10(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-10-25
• Subjects: high latitude -- phytoplankton bloom -- phenology -- remote sensing; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2021JC018346
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Eighteen years (2003–2020) of data on remotely‐sensed ocean color in high northern latitudes show a significant increase (0.56% yr −1 ) in double blooms of phytoplankton. Starting in 2015 the rate of increase rose to 1.10% yr −1 . Double blooms have become especially prevalent in regions north of 50°N in the North Atlantic, Gulf of Alaska and southern Chukchi Sea. Our correlation analysis suggests that double bloom occurrences are dependent on latitude and seasonal changes in both sea surface temperature (SST) and mixed layer depth (MLD), particularly in the subpolar North Pacific (SNP) and polar oceans (65°–75°N), although we cannot attribute the increased double blooms to specific causes. Single blooms indicated by Chlorophyll a (Chl a ) dominate in subpolar‐polar waters and occur close to the timing of the Particulate Inorganic Carbon (PIC) peak (i.e., June–August). In the SNP single bloom, Chl a peaks occur earlier than PIC peaks. This interval was shorter during 2016–2020, which is associated with warming anomalies. In the southern part of the Chukchi Sea, however, we found that PIC peaks occur earlier than Chl a peaks, suggesting a potentially different succession pattern between calcifiers and other functional groups. We speculate that in the near future double blooms of phytoplankton will become a prevalent feature in high‐latitude oceans with concurrent changes in the timing of blooms and seasonal phytoplankton succession in the surface ocean due to climate change. Plain Language Summary: The subpolar and polar oceans are characterized by seasonal phytoplankton blooms during spring–summer. Recently a second bloom attributed to climate change and mostly occurring in fall has been observed. Our study of satellite observations across 18 years (2003–2020) shows that double blooms have been increasing in oceans north of 50°N. The increase in double blooms is related to water temperature and mixed layer depth, but this relationship is dependent on seasons, latitudes and ocean basins. We also compared the timing between two satellite‐derived proxies for the abundance of noncalcifying and calcifying phytoplankton communities. In the subpolar North Pacific (50°–65°N) we found the interval between these two blooms was shorter during 2016–2020, a period associated with warming water. In the southern part of the Chukchi Sea (65°–70°N) we found that the first annual blooms are more likely dominated by calcifying phytoplankton (i.e., coccolithophores) followed by a second blooms with a peak of Chlorophyll a concentration. Our results suggest that with ongoing environmental change, double blooms could become a prevalent feature of the subpolar northern oceans and parts of the Arctic Ocean. Key Points: Satellite data show a significant increase in double blooms of phytoplankton north of 50°N, particularly from 2016 to 2020 The correlation of double blooms with mixed layer depth and sea surface temperature is dependent on latitude and season From 2016 to 2020, the interval between peaks of single PIC and Chl a blooms shortened in the subpolar North Pacific Ocean