Joseph Alphonse Adhémar (1797–1862) was a French

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

. He was the first to suggest that

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

s were controlled by

astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...

forces in his 1842 book ''Revolutions of the Sea''. "Joseph Adhémar seems to have been the first to suggest that glaciation was associated with changes in the configuration of Earth's orbit relative to the Sun. In 1842, he proposed that glaciation ... " The

Earth's orbit Earth orbits the Sun at an astronomical unit, average distance of , or 8.317 light-second, light-minutes, in a retrograde and prograde motion, counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes & ...

is elliptical, with the Sun at one focus; lines drawn through the summer and winter

solstice A solstice is the time when the Sun reaches its most northerly or southerly sun path, excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around 20–22 June and 20–22 December. In many countries ...

; and the spring and autumn equinox; intersect with the Sun at

right angle In geometry and trigonometry, a right angle is an angle of exactly 90 Degree (angle), degrees or radians corresponding to a quarter turn (geometry), turn. If a Line (mathematics)#Ray, ray is placed so that its endpoint is on a line and the ad ...

s. The Earth is closest to the Sun (

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

) near the

northern hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

winter solstice The winter solstice, or hibernal solstice, occurs when either of Earth's geographical pole, poles reaches its maximum axial tilt, tilt away from the Sun. This happens twice yearly, once in each hemisphere (Northern Hemisphere, Northern and So ...

. The Earth moves faster through its

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

when closer to the Sun. Hence, the period from the northern hemisphere's autumn equinox to winter and spring is shorter by around seven days than the period from spring to summer to autumn; the reverse is true in the southern hemisphere. Hence, northern hemisphere winter is shorter. Because of this, Adhemar reasoned that because the southern hemisphere had more hours of darkness in winter, it must be cooling, and attributed the

Antarctic The Antarctic (, ; commonly ) is the polar regions of Earth, polar region of Earth that surrounds the South Pole, lying within the Antarctic Circle. It is antipodes, diametrically opposite of the Arctic region around the North Pole. The Antar ...

ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacier, glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are the Antarctic ice sheet and the Greenland ice sheet. Ice s ...

to this. Adhemar knew of the 22,000 year cycle of

precession of the equinoxes In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's Rotation around a fixed axis, rotational axis. In the absence of precession, the astronomical body's orbit would show ...

, and theorised that the ice ages occurred in this cycle. One immediate objection to the theory was that the total

insolation Solar irradiance is the power per unit area ( surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ...

during a year does not vary at all during the

precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In o ...

al cycle, only its seasonal distribution. Another was that the timing was wrong; however this could not be tested by observations available at the time. Adhemar's theory was further developed, first by James Croll and later by

Milutin Milanković Milutin Milanković (sometimes Anglicisation of names, anglicised as Milutin Milankovitch; sr-Cyrl, Милутин Миланковић, ; 28 May 1879 – 12 December 1958) was a Serbian mathematician, astronomer, climatologist, geophysics, geo ...

. Adhemar predicted the Antarctic ice sheet and theorised about its thickness by comparing the depths of the Arctic and circum-Antarctic oceans. Finding the Antarctic oceans deeper (the measurements he used may not have been fully representative) and attributing this to the gravitational attraction of the Antarctic ice sheet, he postulated a truly enormous ice sheet approximately 90 km thick.

References

Sources

* E. Bard, Greenhouse effect and ice ages: historical perspective; Comptes Rendues Geoscience, 336 (2004) 603-638 (in French and English). {{DEFAULTSORT:Adhemar, Joseph 1797 births 1862 deaths French climatologists 19th-century French earth scientists 19th-century French mathematicians