1 research outputs found
Recommended from our members
Abrupt Younger Dryas cooling in the northern tropics recorded in lake sediments from the Venezuelan Andes.
10 p., 6 fig.[EN] A radiocarbon dated sediment record from Laguna de Los Anteojos, a cirque lake in the Mérida Andes of
Venezuela, indicates that warmer and wetter atmospheric conditions occurred in the northern tropics at the
onset of the Bølling (∼14,600 cal yr BP), and abruptly colder and drier conditions around the time of the
Younger Dryas (YD). Geochemical and clastic sediment analyses from Los Anteojos show that glaciers
advanced at ∼12,850 cal yr BP, reached their YD maximum extent at ∼12,650 cal yr BP, and then retreated
until complete deglaciation of the watershed at ∼11,750 cal yr BP. The onset of warmer conditions that
ended the coldest phase of the YD occurred several hundred years earlier at Los Anteojos than in the high
latitudes of the Northern Hemisphere. During the peak YD glacial advance, glacier equilibrium-line altitudes
in the region were ∼360 to 480 m lower, and temperature was ∼2.2 to 2.9 °C colder than modern.
Independent palynological evidence from the Los Anteojos sediment core indicates that the northern Andes
were more arid and at least 2.3 °C colder during the YD. The direction and timing of glacial fluctuations in
Venezuela are consistent with observations of marine sediment records from the Cariaco Basin that suggest
abrupt cooling occurred at ∼12,850 cal yr BP, followed by a shift to higher temperature after ∼12,300 cal yr
BP. The timing and pattern of climatic changes in northern South America are also consistent with
paleoclimate records from the southern Tropical Andes that suggest a southward shift in the position of the
Intertropical Convergence Zone occurred at the start of the cooling event, followed by a return to wetter
conditions in northern South America during the late stages of the YD. The early warming of the tropical
atmosphere and invigoration of the hydrologic cycle likely contributed to the shift to increased temperature
in the higher latitudes of the Northern Hemisphere at the end of the late Glacial stage.Peer reviewe