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Twentieth century warming in deep waters of the Gulf of St. Lawrence: A unique feature of the last millennium
Author(s) -
Thibodeau Benoît,
de Vernal Anne,
HillaireMarcel Claude,
Mucci Alfonso
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl044771
Subject(s) - oceanography , water mass , benthic zone , estuary , global warming , climate change , deep water , geology , little ice age , isotopes of oxygen , environmental science , climatology , physical geography , geography , geochemistry
The impact of human activities on Earth's climate is still subject to debate and the pattern of a sharp recent global temperature increase contrasting with much lesser variable temperatures during preceding centuries has often been challenged, partly due to the lack of unquestionable evidence. In this paper, oxygen isotope compositions of benthic foraminifer shells recovered from sediments of the Lower St. Lawrence Estuary and the Gulf are used to reconstruct temperature changes in a water mass originating from ∼400 m deep North Atlantic waters. The data demonstrate that the 1.7 ± 0.3°C warming measured during the last century corresponds to a δ 18 O shift of 0.4 ± 0.05‰, encompassing the temperature effect and related change in the isotopic composition of the corresponding water mass. In contrast, δ 18 O values remained nearly constant over the last millennium, except for a small positive shift which we attribute to the Little Ice Age. We conclude that the 20th century warming of the incoming intermediate North Atlantic water has had no equivalent during the last thousand years.