Ocean colour changes in the North Pacific since 1930

M R Wernand,H.~J.~Van Der Woerd

doi:10.2971/jeos.2010.10015s

Abstract

In this paper we present an analysis of historical ocean colour data from the North Pacific Ocean. This colour is described by the Forel-Ule colour index, a sea colour comparator scale that is composed of 21 tube colours that is routinely measured since the year 1890. The main objective of this research is to characterise colour changes of the North Pacific Ocean at a timescale of lustums. Next to the seasonal colour changes, due to the yearly cycle of biological activity, this time series between 1930 and 1999 might contain information on global changes in climate conditions. From seasonal independent analyses of the long-term variations it was found that the greenest values, with mean Forel-Ule scale, FU¯, of 4.1 were reached during the period of 1950–1954, with a second high (FU¯ = 3) in the period 1980–1984. The bluest ocean was encountered during the years 1990–1994. The data indicate that after 1955 a remarkable long bluing took place till 1980.

Highlights

In 1992, the physical oceanographer Bruce Parker investigated the retrieval of historical oceanographic data and emphasized the importance of the so-called oceanographic “data archaeology” [1]
In this paper we present an analysis of historical ocean colour data from the North Pacific Ocean
This colour is described by the Forel-Ule colour index, a sea colour comparator scale that is composed of 21 tube colours that is routinely measured since the year 1890

Summary

Introduction

In 1992, the physical oceanographer Bruce Parker investigated the retrieval of historical oceanographic data and emphasized the importance of the so-called oceanographic “data archaeology” [1] He stated that “a critical requirement for climate and global change research is the availability of global oceanographic data covering long time periods”. The colour of the ocean surface waters is one of parameters that is described for more than 3 centuries [2] and one that is measured quantitatively since the year 1890 [3]. Venrick et al [14] found a significant increase in total chlorophyll-a, during the summer, over a 20 year time span in the central North Pacific Ocean and concluded in Nature (1987) that long-period fluctuations in atmospheric characteristics (decrease in sea surface temperature, increase in wind forcing in winter) changed the carrying capacity of the central Pacific Pelagic ecosystem

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