Temporal variability of satellite-retrieved chlorophyll-a data in Arctic and subarctic ocean regions within the past two decades

ABSTRACT

Two decades (1997–2017) of blended satellite-retrieved phytoplankton chlorophyll a concentration (Chl-a) data were used to assess the interannual variation and recent trends of phytoplankton biomass in Arctic and subarctic ocean (ASAO) regions. Satellite and reanalysis data for geophysical variables were used to assess the probable environmental factors responsible for the observed Chl-a changes. Aggregate Chl-a in the entire ASAO increased steadily from 1997 and then began to decline in the early 2010s. This decline reflects Chl-a declines in most ASAO regions, but the responsible factors and the year in which the trend reversal occurred varied greatly from region to region. In open ocean regions, large-scale climate variability might underlie the Chl-a decline, whereas, in semi-enclosed coastal waters and embayments, the underlying factors might be local or regional (including land–ocean interactions). Therefore, although sea surface temperatures in the ASAO continued to increase steadily, the decline in aggregate Chl-a in the ASAO is unlikely to be connected to global warming.

KEYWORDS:

• remote sensing
• phytoplankton
• climate change
• land-ocean-atmosphere interactions

Acknowledgements

This study was supported by a grant (CAF2017-02CMY-Siswanto) from the Asia–Pacific Network for Global Change Research. I am grateful to two anonymous reviewers for their constructive and valuable comments. For processing and distributing the primary datasets, I thank the Ocean Colour-Climate Change Initiative Project (Chl-a and R_RS; (https://esa-oceancolour-cci.org/), the GlobColour Project (PAR; http://www.globcolour.info/), the National Snow and Ice Data Center (SIC; https://nsidc.org/), and the Copernicus Marine Environment Monitoring Service (SST and MLD; http://marine.copernicus.eu/). Additional Chl-a datasets processed and distributed by the NASA Ocean Biology Processing Group (https://oceancolor.gsfc.nasa.gov/) and the GlobColour Project (http://www.globcolour.info/) were also used.

Disclosure statement

The author reports no potential conflict of interest.

Additional information

Funding

This work was supported by the Asia-Pacific Network for Global Change Research (APN, CAF2017-02CMY-Siswanto), a project under the APN Climate Adaptation Framework (CAF) Program; Asia-Pacific Network for Global Change Research (APN) [CAF2017-RR02-CMY-Siswanto].