摘要
There has been a long history of interest on how(if)the absorption coefficient of“pure”fresh water(a_(fw)(λ))and“pure”seawater(a_(sw)(λ))changes with temperature(T),yet the impact of T reported in the literature differs significantly in the blue domain.Unlike the previous studies based on laboratory measurements,we took an approach based on~18 years(2002–2020)of MODIS ocean color and temperature measurements in the oligotrophic oceans,along with field measured chlorophyll concentration and phytoplankton absorption coefficient,to examine the relationship between T and the total absorption coefficient(a(λ))at 412 and 443 nm.We found that the values of a(412)and a(443)in the summer are nearly flat(slightly decreasing)for the observed T range of~19–27℃.Since there are no detectable changes of chlorophyll during this period,the results suggest that T has a negligible impact on a_(sw)(412) and a_(sw)(443)in this T range.As a complement,the impact of salinity on a_(fw)(λ) was also evaluated using three independent determinations of a_(sw)(λ) and a_(fw)(λ),where good agreements were found from these observations.
基金
support provided by the National Natural Science Foundation of China(#41890803,#41941008,and#41830102)
the Joint Polar Satellite System(JPSS)funding for the NOAA ocean color calibration and validation(Cal/Val)project(SA18-UMB01)
the University of Massachusetts Boston is greatly appreciated
NASA OBPG for processing and providing global MODIS ocean color data and the Hawaii Ocean Time-series HOT-DOGS application(University of Hawai’i at Mānoa,National Science Foundation Award#1756517)for data collection and sharing。
