• francisco.machin@ulpgc.es

On this day in history...

...in 1861, Fridtjof Nansen was born in Store Frøen, near Christiania (now Oslo), Norway. The son of a family of jurists with a deep connection to nature, Nansen grew up in an environment that cultivated both intellectual rigor and outdoor life. He studied zoology at the Royal Frederick University in Christiania and earned his doctorate with a thesis on the central nervous system of marine animals, contributing to the foundations of modern neurology even before turning his career toward the ocean. Yet, it was the sea that would ultimately claim him.

Fridtjof Nansen

The expedition aboard the Fram between 1893 and 1896 marked a turning point not only in the history of polar exploration but also in the development of oceanography as a scientific discipline. Nansen’s plan was as bold as it was methodical: allow the ship to be deliberately trapped in the pack ice of the East Siberian Sea and let itself be carried by the transpolar drift toward the north. Far from a blind gamble, the strategy was supported by Henrik Mohn’s hypothesis about the existence of a current crossing the Arctic Ocean from east to west, backed by debris from the USS Jeannette found on the shores of Greenland. During three years of drift, Nansen and his crew turned that icy prison into an oceanographic observatory: they measured temperatures and salinities at various depths, documented the stratification of the Arctic Ocean with a cold, low-salinity surface layer abruptly separated from deeper, warmer, saltier waters, and recorded that icebergs moved at a systematic angle to the right of the prevailing wind—an observation that Nansen could not explain at the time but that planted the seed for one of the central concepts of physical oceanography.

That observation, passed on to Vilhelm Bjerknes, reached the young Vagn Walfrid Ekman, who formalized it in his 1905 paper introducing the Ekman Spiral. The Fram expedition not only generated the data that fed this discovery; Nansen also designed, during the voyage preparations, the bottle that bears his name. Invented in 1894 and described in detail in his 1902 publication The Oceanography of the North Polar Basin, the Nansen bottle allowed, for the first time, the collection of water samples at precise depths without contamination from the upper water column. A metal messenger descended along the wire and, upon striking the bottle, inverted it, simultaneously closing valves at both ends and fixing the reading of the reversing thermometer. The design was so effective that it remained a global oceanography standard for more than seven decades, until Shale Niskin developed his plastic version in 1966.

Upon his return, Nansen permanently turned his career toward physical oceanography. In 1909, together with Bjørn Helland-Hansen, he published The Norwegian Sea: Its Physical Oceanography, a monograph built on four years of campaigns with the vessel Michael Sars. The work described the structure of water masses, circulation, and currents of the Norwegian Sea and the Nordic Seas with such detail that its analyses were not fundamentally surpassed for decades. The surface circulation map from that publication, which detailed the route of Atlantic waters northward through the Norwegian Sea to the Barents Sea and Svalbard, remains a reference synthesis in regional oceanography. The work also established the dynamic method for calculating currents from density profiles—a technique that, developed from Bjerknes’s work, became a standard tool in observational oceanography.

Nansen’s contributions to physical oceanography span complementary dimensions:

  • Systematic observation of the Arctic: The Fram expedition provided the first detailed hydrographic characterization of the Arctic basin, including the discovery of the Arctic halocline and the documentation of Atlantic waters at intermediate depths beneath the surface layer.
  • Nansen bottle: An instrument that revolutionized hydrographic sampling by enabling water collection and precise in-situ temperature measurement at specific depths, making systematic analysis of deep-ocean water masses possible for the first time.
  • Seed of the Ekman Spiral: The observation of the angular deviation of icebergs relative to the wind was the empirical starting point that led Ekman to formulate the theory of the wind’s effect on ocean currents in the presence of the Coriolis force.
  • Oceanography of the Nordic Seas: The 1909 monograph with Helland-Hansen established the canonical description of the circulation and water masses of the Norwegian Sea, with direct implications for understanding heat and salt exchange between the North Atlantic and the Arctic Ocean.
  • Deep water formation model: Based on his observations in the Greenland Sea, Nansen in 1906 proposed the classic model for the formation of Greenland Sea Deep Water through winter convection—a key process in the global thermohaline circulation.

Nansen never separated direct observation from theoretical thought, and this combination permeates all his work. He was the one who trained Helland-Hansen, guided Ekman, and transformed the raw data from three years of Arctic drift into the foundation of a discipline. His figure also transcends the laboratory: he received the Nobel Peace Prize in 1922 for his humanitarian work with refugees of World War I—a dimension of his career that does not overshadow but complements that of a scientist who understood the observation of the natural world as an act of responsibility.

Sources

Reference date
10 Oct

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