Todd Glacier () is a

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

7 nautical miles (13 km) long flowing southwest into

Calmette Bay Calmette Bay () is a small bay between Camp Point and Cape Calmette, on the west coast of Graham Land. It was charted by the British Graham Land Expedition under John Rymill John Riddoch Rymill (13 March 1905 – 7 September 1968) was an Aus ...

, western

Graham Land Graham Land is the portion of the Antarctic Peninsula that lies north of a line joining Cape Jeremy and Cape Agassiz. This description of Graham Land is consistent with the 1964 agreement between the British Antarctic Place-names Committee ...

. It was photographed from the air by

Ronne Antarctic Research Expedition The Ronne Antarctic Research Expedition (RARE) was an expedition from 1947–1948 which researched the area surrounding the head of the Weddell Sea in Antarctica. Background Finn Ronne led the RARE which was the final privately sponsored exp ...

(RARE), 1947. Surveyed by

British Antarctic Survey The British Antarctic Survey (BAS) is the United Kingdom's national polar research institute. It has a dual purpose, to conduct polar science, enabling better understanding of list of global issues, global issues, and to provide an active prese ...

(BAS), 1961–62. Named by

United Kingdom Antarctic Place-Names Committee The UK Antarctic Place-Names Committee (or UK-APC) is a United Kingdom government committee, part of the Foreign and Commonwealth Office, responsible for recommending names of geographical locations within the British Antarctic Territory (BAT) and ...

(UK-APC) for Gertrude E. Todd, BAS Scientific Officer and Editor, employed in the London Office, 1950–63.

Geographical setting

Todd Glacier descends from the northern flank of the Todd Icefield (located at approximately 56° 13' N, 129° 46' W) and feeds the head of north-facing Todd Valley in the

Boundary Ranges The Boundary Ranges, also known in the singular and as the Alaska Boundary Range, are the largest and most northerly subrange of the Coast Mountains. They begin at the Nass River, near the southern end of the Alaska Panhandle in the Canadian pro ...

of north-western

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

. Until the mid-20th century its

tongue The tongue is a Muscle, muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for chewing and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper s ...

merged with four neighbouring tributary glaciers, the composite snout ending about 2.5 km down-valley at roughly 1000 m elevation;

meltwater Meltwater (or melt water) is water released by the melting of snow or ice, including glaciers, glacial ice, tabular icebergs and ice shelf, ice shelves over oceans. Meltwater is often found during early spring (season), spring when snow packs a ...

gives rise to Todd Creek, which drains to the

Portland Canal Portland Canal is an arm of Portland Inlet, one of the principal inlets of the British Columbia Coast. It is approximately long. The Portland Canal forms part of the border between southeastern Alaska and British Columbia. The name of the enti ...

fjord system. Since the 1970s every glacier in the valley has thinned and retreated, with aerial photographs showing terminus recession rates of roughly 9–76 metres per year between 1974 and 1997; Recession has exposed a fluted till forefield, small recessional

moraine A moraine is any accumulation of unconsolidated debris (regolith and Rock (geology), rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a gla ...

s, deeply incised meltwater channels and steep lateral-moraine walls that rise to the

Little Ice Age The Little Ice Age (LIA) was a period of regional cooling, particularly pronounced in the North Atlantic region. It was not a true ice age of global extent. The term was introduced into scientific literature by François E. Matthes in 1939. Mat ...

trimline The Trimline telephone is a series of telephones that was produced by Western Electric, the manufacturing unit of the Bell System. These telephones were first introduced in 1965 and are formally referred to as the ''No. 220 Hand Telephon ...

(roughly 1200 m)—the valley-side boundary showing the glacier's maximum thickness during that period.

Glaciological history

Dendroglaciological and

radiocarbon Carbon-14, C-14, C or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic matter is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...

studies carried out in the forefields of Todd, Two, Sage and Bug glaciers, together with work on the adjacent

Surprise Glacier Surprise (or, rarely, surprize) may refer to: * Surprise (emotion), a brief emotional state experienced as the result of an unexpected significant event Places * Surprise, Arizona, a city in the United States * Surprise, Indiana, an unincorporat ...

moraine, reveal a detailed late-

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

record. Five principal advance intervals are recognised: (1) a pre-Tiedemann event older than 3000 ¹⁴C yr BP (¹⁴C yr BP = radiocarbon years before present, where "present" is conventionally AD 1950); (2) the regional Tiedemann advance at ~3000 ¹⁴C yr BP; (3) a lesser-known expansion about 2300 ¹⁴C yr BP; (4) a two-phase First-Millennium advance centred on ~1700 and ~1450 ¹⁴C yr BP; and (5) a multi-stage Little Ice Age sequence that began before 750 ¹⁴C yr BP and culminated in two late bursts after roughly AD 1760 and around AD 1900. The work hinges on

tree ring Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed in a tree. As well as dating them, this can give data for dendroclimatology, the study of climate ...

cross-dating of ''in situ'' stumps and detrital boles, supplemented by perimeter-ring radiocarbon ages, allowing individual kill events to be tied to glacier margins with annual precision. During the early Little Ice Age (roughly AD 883–1156) Two and Sage glaciers had already coalesced with Todd Glacier, filling the trunk valley; by 730–660 ¹⁴C yr BP the combined front stood at the present forefield, as shown by buried forest horizons. Subsequent readvances in the eighteenth century felled trees on Surprise Glacier's lateral moraine (perimeter years 1746 and 1764), while a final surge in 1898–1899 pushed over mature subalpine

fir Firs are evergreen coniferous trees belonging to the genus ''Abies'' () in the family Pinaceae. There are approximately 48–65 extant species, found on mountains throughout much of North and Central America, Eurasia, and North Africa. The genu ...

on the west wall of Two-Glacier Valley. These events mark the greatest documented Holocene extent of the Todd Glacier system; the pronounced 20th-century retreat described above therefore represents a dramatic reversal from that late Little Ice Age maximum.

References

{{Glaciers of Graham Land Glaciers of Fallières Coast