Publication Date:
2019-12-05
Description:
Satellite remote sensing of chlorophyll a concentration (Chl-a) in the Arctic Ocean
is spatially and temporally limited and needs to be supplemented and validated with
substantial volumes of in situ observations. Here, we evaluated the capability of obtaining
highly resolved in situ surface Chl-a using underway spectrophotometry operated during two
summer cruises in 2015 and 2016 in the Fram Strait. Results showed that Chl-a measured
using high pressure liquid chromatography (HPLC) was well related (R2 = 0.90) to the
collocated particulate absorption line height at 676 nm obtained from the underway
spectrophotometry system. This enabled continuous surface Chl-a estimation along the cruise
tracks. When used to validate Chl-a operational products as well as to assess the Chl-a
algorithms of the aqua moderate resolution imaging spectroradiometer (MODIS-A) and
Sentinel-3 Ocean Land Color Imager (OLCI) Level 2 Chl-a operational products, and from
OLCI Level 2 products processed with Polymer atmospheric correction algorithm (version
4.1), the underway spectrophotometry based Chl-a data sets proved to be a much more
sufficient data source by generating over one order of magnitude more match-ups than those
obtained from discrete water samples. Overall, the band ratio (OCI, OC4) Chl-a operational
products from MODIS-A and OLCI as well as OLCI C2RCC products showed acceptable
results. The OLCI Polymer standard output provided the most reliable Chl-a estimates, and
nearly as good results were obtained from the OCI algorithm with Polymer atmospheric
correction method. This work confirms the great advantage of the underway
spectrophotometry in enlarging in situ Chl-a data sets for the Fram Strait and improving
satellite Chl-a validation and Chl-a algorithm assessment over discrete water sample analysis
in the laboratory.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
peerRev
Format:
application/pdf
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