Bernacchi was born in Belgium on 8 November 1876 to Italian parents. His father, Diego Bernacchi, established a vineyard on Maria Island in 1884. He was educated in Hobart, Tasmania, at the Hutchins School. He entered the Melbourne Observatory in 1895 where he spent about three years studying magnetism and meteorology. During this period he developed an interest in Antarctic exploration, expressed in letters to the press and by following the proceeding of Antarctic Exploration Committees.
Polar exploration
He joined Carstens Borchgrevink's Southern Cross expedition which wintered at Cape Adare, Antarctica, joining the expedition in New Zealand after the previous physicist candidate had been rejected on medical grounds. The expedition was the first to spend the winter on the Antarctic continent and the first to sledge towards the South Pole. He wrote a book about the expedition To the south polar regions: expedition of 1898-1900 published in 1900. His granddaughter Janet Crawford has edited a version of his diaries from the expedition under the title That First Antarctic Winter: The story of the Southern Cross Expedition of 1898-1900. He was again a physicist on the Discovery expedition led by Robert Falcon Scott. Bernacchi was the only man on this expedition who had previously been to the Antarctic. During the trip, he made extensive magnetic observations. Following the trip, Bernacchi was awarded the Royal Geographical Society and King's Antarctic Medal as well as the Légion d'honneur. Scott was the best man at Bernacchi's marriage in 1906.
Three landmarks in Antarctica are named after him: Bernacchi Head, on Franklin Island, Cape Bernacchi and Bernacchi Bay, both on the coast of Victoria Land. A species of Antarctic fish, the Trematomus bernacchii was named in his honor. In 2001, Australia Post issued a postal stamp in honour of the 100th anniversary of Australia's involvement in Antarctic exploration. The Premier of Tasmania, Jim Bacon, unveiled sculptures of Bernacchi and fellow explorers at Sullivans Cove.
Writings
The South polar times. London: Smith, Elder & co., 1907-1914. An exact reproduction of the South polar times originally issued during the Antarctic expeditions of Robert F. Scott.
Saga of the "Discovery". London: Glasgow, Blackie and son, Ltd. : Re-printed by Rooster Books Ltd
To the south polar regions: expedition of 1898-1900. By Louis Bernacchi; introduction by D.W.H. Walton. Denton, Harleston, Norfolk: Bluntisham Books : Erskine Press, 1991.
A very gallant gentleman. London: T. Butterworth, ltd. .
That first Antarctic winter : the story of the Southern Cross Expedition of 1898-1900 as told in the diaries of Louis Charles Bernacchi / written and edited by Janet Crawford. Christchurch, N.Z.: South Latitude Research Ltd., in association with P.J. Skellerup, c1998.