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, structure, space, models, and change. History On ...

. 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 gree ...

s were controlled by astronomical 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 average distance of 149.60 million km (92.96 million mi) in a counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes days (1 sidereal year), during which time Earth ...

elliptical Elliptical may mean: * having the shape of an ellipse, or more broadly, any oval shape ** in botany, having an elliptic leaf shape ** of aircraft wings, having an elliptical planform * characterised by ellipsis (the omission of words), or by conc ...

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

solstice A solstice is an event that occurs when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. In many countr ...

; and the

spring Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of water * Spring (mathematics), a geometric surface in the shape of a ...

and

autumn equinox Autumnal equinox or variations, may refer to: * September equinox, the autumnal equinox in the Northern Hemisphere * March equinox, the autumnal equinox in the Southern Hemisphere Other uses * Autumnal Equinox Day (Japanese: 秋分の日, ''Shūbu ...

; 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) 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 as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

winter solstice The winter solstice, also called the hibernal solstice, occurs when either of Earth's poles reaches its maximum tilt away from the Sun. This happens twice yearly, once in each hemisphere ( Northern and Southern). For that hemisphere, the winte ...

. The earth moves faster through its

orbit In celestial mechanics, an orbit 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 object or position in space such as a p ...

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 ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...

ice sheet 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 rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. In particu ...

, 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 (W/m ...

during a year does not vary at all during the precessional 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 James Croll, FRS, (2 January 1821 – 15 December 1890) was a 19th-century Scottish scientist who developed a theory of climate variability based on changes in the Earth's orbit. Life James Croll was born in 1821 on the farm of Little Whitefi ...

and later by

Milutin Milanković Milutin Milanković (sometimes anglicised as Milankovitch; sr-Cyrl, Милутин Миланковић ; 28 May 1879 – 12 December 1958) was a Serbian mathematician, astronomer, climatologist, geophysicist, civil engineer and popularizer of ...

. 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 In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong ...

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 mathematicians