Digital Archive

Light, color and clarity are intriguing features that drove philosophical and scientific investigations throughout the history

The same holds true for mankind’s fascination for the sea. Thus it is not astounding that the combination of both sea and light, the field of ocean colour observations, has a long record of innovations and applications. Yet these insights are sometimes hidden in paper archives and long forgotten publications, thus not accessible to the broader community.

Within this digital archive we included numerous publications from the discipline of ocean optics that we extracted and referenced from historic documents. Thus offering a glance on the past of optics in the sea, we hope to support todays researcher in pursue of gaining new insights and clarity. It is not only a joy to read historic quotes, scientific travels, exploration of parts of the world and the design of the earliest Marine optical instruments.

Marcel Wernand

Dr. Marcel R. Wernand
Royal Netherlands Institute for Sea Research
Coastal Systems, Marine Optics & Remote Sensing
PO box 59. 1790AB Den Burg, Texel, The Netherland

Historic Notes

The foureteenth, in the morning, was calme with fogge. At nine, the wind at east, a small gale with thicke fogge ; wee steered south-eastand by east, and running this course we found our greene sea againe, which by proofe we found to be freest from ice, and our azure blue sea to be our ice sea. At this time we had more birds then we usually found.
H. Hudson, First voyage, 1607

For thence it may be gather'd, that the Sea-Water reflects back the violet and blue- Making Rays most easily, and lets the red-making Rays pass, most freely and copiously to great Depths. For thereby the Sun's direct Light at all great Depths, by reason of the predominating redmaking Rays, must appear red; and the greater the Depth is, the fuller and in-tenser must that red be. And at such Depths as the violet-making Rays scarce penetrate unto, the blue-making, green-making, and yellow making Rays being reflected from below more copiously than the red- making ones, must compound a green.
I. Newton, 1704

Alles, was sich auf die Farbe des Wassers bezieht, ist ausnehmend problematisch.
A. Von Humboldt, 1815

The colour of the Greenland Sea varies from ultramarine blue to olive green, and from the most pure transparency to striking opacity. These appearances are not transitory, but permanent; not depending on the state of the weather, but on the quality of the water. Hudson, when he visited this quarter in the year 1607, noticed the changes in the colour of the sea, and made-the observations, that the sea was blue where there was ice, and green where it was most open.
W. Scoresby, 1820

Mit dem Spectroskop untersucht, zeigte sich in dem aus dem Wasser kommenden Licht das Roth ganz verschwunden, das Gelb sehr erheblich verblaßt, so daß die D- Linie kaum zu erkennen war, dagegen erschienen Grün, Blau und Indigo hell und die beiden Linien E und b flossen zu einem deutlichen dicken Absorptionsstreifen zusammen. Meine Absicht, auch das Licht der 'grünen' Grotte zu untersuchen, konnte ich leider wegen plötzlicher Erkrankung nicht ansführen; jedenfalls dürfte sich aber solches der Mühe verlohnen und möchte ich durch diese Notiz Veranlassung geben, das Spectroskop bei Untersuchung der noch in vielen Stücken räthselhaften Wasserfärbung mehr als bisher zu benuntzen.
H. W. Vogel, 1875

La question est depuis longtemps posee : ä quoi tiennent ces differences de couleur? Pour etudier systematiquement la couleur des lacs, j'ai employe deux methodes d'observation : La premiere consiste ä prendre la note de la nuance ou du ton avec des craies de pastel frottees sur un carton grisatre. Aussi ai-je cherche une autre methode. Je me suis fait une gamme de couleurs transparentes en adoptant la disposition suivante: Je fais deux solutions aqueuses, l'une bleue, de sulfate de cuivre ammoniacal, l'autre de chromate neutre de potassium, l'une et l'autre au 1 : 200e.
F. A. Forel, 1895

Wer nur Ost- und Nordsee befahren hat, vermag sich keine Vorstellung von dem satten, tiefen und doch auch hellen Blau zu machen, das dem Wasser gewisser zentraler Teile des Atlantischen Ozeans eigen ist. Schnars-Alquist hat uns in herrlichen, künstlerisch und man darf sagen auch wissenschaftlich vollendeten Gemälden das Blau des Ozeans gezeigt (Fig. 1), das manchem Beschauer unnatürlich erscheint.
G. Schott, 1911

A sufficient deep layer of pure water exhibits by molecular scattering a deep blue colour more saturated than sky-light and of comparable intensity. The colour is primarily due to diffraction, the absorption only making it of a fuller hue. The theories hitherto advanced that the dark blue of the deep sea is reflected sky-light or that it is due to suspended matter are discussed and shown to be erroneous.
C. Raman, 1922

These quotes indicate that the colour of the sea has been an intriguing phenomenon since the days of Hudson, and probably much earlier. Through time the everchanging colours of lakes and seas amazed travellers, and inspired painters and writers. At a later stage scientists interested in an explanation of the phenomenon became aware of the fact that the sea colour and its transparency could be related to "what's in the water", i.e. organic and inorganic material, which apparently determined its colour.

Already William Hudson, explorer of the sea and navigator of the early 17th century, was aware of the fact that changing sea colours meant change in bottom topography; therewith the observation of 'colour' was useful for navigation purposes. Goethe described the colour of the sea during his crossing from Messina to Naples in 1739 in his book 'Voyage to Italy' (Goethe, 1786). For him, like many others, it was merely a joy to look at the variable colours of the sea. In figurative art that is inspired the sea we usually see beautiful, but most of all colourful seascapes.

A painting of a realistically depicted sea by Prof. Hugo Schnars-Alquist (1855-1939), marine painter, titled Marine (1906), is a good example. During the attempts to explain the colour and transparency of the sea, scientists designed devices to measure and classify these water properties.

Acknowledgments

Looking for and ordering publications, writing the bibliography: 
Leonne van der Weegen, Marlies Bruining, Jeroen Bos from the Library of the Royal Netherlands Institute for Sea Research

Design & Code:
Arjan Hemelrijk and Olivier Schilling from Veerder, Texel, NL

Providing webspace for the historic archive: 
Prof. Dr. Oliver Zielinski, director of the Institute for Chemistry and Biology of the Marine Environment ICBM, Research Group Marine Sensor Systems (Carl von Ossietzky University, Oldenburg, DE), coordinator of the Coastal Ocean Darkening project.
 

Prof. Hugo Schnars-Alquist's oil on canvas, Marine (1906), is a good example of a realistically painted sea.

Clarity on the Sea - Coastal Ocean Darkening