Figure 1.
Krümmel's contoured North Atlantic FU-map (1889).
The sailing track of the steamship ‘National’ is shown in black. The colour (Wasserfarbe) was indicated as a percentage of a yellow potassium chromate solution added to a blue copper-sulphate solution. The legend indicates the FU-scale colours 1 to 21.
Figure 2.
The temporal distribution of the total number of 221110 FU-observations contained within dataset-0 for the period 1889 to 1999.
Data is binned per season and per decade except for the first period of 11 years from 1889–99. Notice: the period 1900 to 1929 contain zero or a limited number of observations.
Table 1.
The distribution of FU-observations contained within dataset-1.
Figure 3.
Example (around Japan) of three defined masks to extract FU-observations; in white the BM1 mask starting at the land/sea boundary spreading over the whole sea with on top of this layer, in dark grey, BM2 starting at a distances of >100 km off land and on top of this layer BM3, a layer in black, starting at a distance of 500 km off land.
Table 2.
The number of FU-observations per dataset unmasked and obtained by the use of 3 data-extraction masks.
Table 3.
Specifications of the four components used in the Ecolight model for concentration ranges, inherent optical properties and atmosphere.
Figure 4.
The positions of FU-observations extracted at a distance >500 km off-coast and at a distance of >100 km off-coast (resp.21971 obs.▴, 61434 obs.▵).
Oceans and seas are indicated by abbreviations as mentioned in Table 2. Red lines indicate the division of north and equatorial regions. Although the Mediterranean has a limited number of 237 observations, it was found to be important to analyse this sea for which data were already collected at the end of the 19th century.
Figure 5.
The selected 21302 FU-observations extracted under the ocean mask BM3, binned per sea area and per season.
Figure 6.
The selected 67581 FU-observations extracted under the basin mask BM2, binned per sea area and per season.
Figure 7.
Examples of the Ecolight modelled RRS (sr−1) for case 1 waters (panel a) and case 2 waters (panels b, c and d) with variable composition (see also Table 4).
In panel (a) only the input chlorophyll concentration is varied between 0.1 and 40 mg m−3. For case 2 waters the input CDOM440 absorption (a440) is varied between 0.01 and 1.00 m−1 with chlorophyll and mineral concentration of both 0 (panel b), fixed chlorophyll concentration of 0.1 mg m−3 and a mineral concentration of 0 (panel c) and fixed chlorophyll concentration of 0.1 mg m−3 and a mineral concentration of 0.2 g m−3 (panel d). From these RRS spectral signatures the chromaticity coordinate set and FU number were calculated.
Figure 8.
Chlorophyll concentration and CDOM attenuation at 440 nm as a function of FU-number.
The FU-numbers were derived from the Ecolight RRS spectra. In the left panel (A), chlorophyll was varied from 0.1 to 40 mg m−3 with a resulting span of FU1 to FU10. For case 2 waters (panel B), the relationship between CDOM and FU was calculated for three combinations of chlorophyll concentration (0 or 0.1 mg m−3) and mineral concentration (0 or 0.2 g m−3).
Figure 9.
Representation of North Atlantic monthly and chlorophyll for the periods 1889–1999 (a) and 1980–1990 (b, only chlorophyll).
a – The BM2 (circles) and BM3 (squares) extracted FU data with error bars show the same pattern and reveal the North Atlantic spring bloom. On the secondary axes, indicated with green line/circles, the modelled chlorophyll (see Eq. 1) with error bars is shown. b – The modelled chlorophyll for the period 1980–1991, compared to CZCS- (1979–1988) and SeaWiFS (1997–2000) derived chlorophyll, blended with in-situ data, as presented by Gregg and Conkright, 2002).
Figure 10.
A global IDW interpolation of BM1 clipped FU observations.
The weight is set to a power of 2. The search radius is set to 4 degrees with an output grid size of 0.5 degrees. Data collection period covers 1889 to 1999.
Figure 11.
Representation of the oceans and seas identified and arranged in terms of their colour as calculated from all available observations extracted under BM2 or BM3 (see
Table 4). The Barents Sea is the most greenish sea (bottom) and the Equatorial Pacific is the most bluish ocean (top).
Figure 12.
An entire MODIS mission composite map of the CDOM Index and chlorophyll-a concentration (4 July 2002–30 Jun 2010).
The map shows a CDOM index <0.5 with the lowest oceanic chlorophyll concentrations of ≈ 0.02 mg m−3 in the South Pacific (white box left). The small white box at the top indicates the open water of the Barents Sea with a CDOM index ≈3.5 and chlorophyll concentrations ≈ 5 mg m−3. Source: level 3 browse, http://oceancolor.gsfc.nasa.gov/.
Figure 13.
Ocean trends: The arithmetic mean derived chlorophyll concentration per year (with the no. of obs.) with superposed lines: weighted (no. of obs.) least-squares regression lines (blue or green line) indicate a bluing trend or greening trend of a sea, the 95% confidence interval of the mean (dotted line) and of the observations (solid line).
A sea with no significant trend is indicated by a black line. Regression coefficients are indicated at the top of each graph.
Figure 14.
Ocean trends: the arithmetic mean derived chlorophyll concentration per year (with the no. of obs.) with superposed lines; weighted (no. of obs.) least-squares regression lines (blue or green line) indicate a bluing trend or greening trend of a sea, the 95% confidence interval of the mean (dotted line) and of the observations (solid line).
A sea with no significant trend is indicated by a black line. Regression coefficients are indicated at the top of each graph.
Table 4.
Results of the weighted linear regression modelling and the Mann-Kendall trend test for the oceans.
Figure 15.
Sea trends: the arithmetic mean FU values () per year (with the no. of obs.) with superposed lines; weighted (no. of obs.) least-squares regression lines (blue or green line) indicate a bluing trend or greening trend of a sea, the 95% confidence interval of the mean (dotted line) and of the observations (solid line).
A sea with no significant trend is indicated by a black line. Regression coefficients are indicated at the top of each graph.
Figure 16.
Sea trends: the arithmetic mean FU values () per year (with the no. of obs.) with superposed lines; weighted (no. of obs.) least-squares regression lines (blue or green line) indicate a bluing trend or greening trend of a sea, the 95% confidence interval of the mean (dotted line) and of the observations (solid line).
A sea with no significant trend is indicated by a black line. Regression coefficients are indicated at the top of each graph.
Table 5.
Results of the weighted linear regression modelling and the Mann-Kendall trend test for the seas.
Table 6.
The Mediterranean weighted linear regression with modelled chlorophyll, assuming an oligotrophic (case 1) classification.