Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Seasonality in equatorial climate over the past 25 k.y. revealed by oxygen isotope records from Mount Kilimanjaro
AU - Barker, Philip A.
AU - Hurrell, Elizabeth R.
AU - Leng, Melanie J.
AU - Wolff, Christian
AU - Cocquyt, Christine
AU - Sloane, Hilary J.
AU - Verschuren, Dirk
N1 - Dec Seasonality in equatorial climate over the past 25 k.y. revealed by oxygen isotope records from Mount Kilimanjaro Times Cited: 0
PY - 2011/12
Y1 - 2011/12
N2 - Multiproxy analysis of a well-dated 25 ka lake sediment sequence from Lake Challa, on the eastern flank of Mount Kilimanjaro (East Africa), reveals the climatic controls that govern both the lake's paleohydrology and the climate-proxy record contained in the mountain's receding ice cap. The oxygen isotope record extracted from diatom silica (delta(18)O(diatom)) in Lake Challa sediments captured dry conditions during the last glacial period and a wet late-glacial transition to the Holocene interrupted by Younger Dryas drought. Further, it faithfully traced gradual weakening of the southeastern monsoon during the Holocene. Overall, delta(18)O(diatom) matches the branched isoprenoid tetraether (BIT) index of rainfall-induced soil runoff, except during 25-22 ka and the past 5 k.y. when insolation forcing due to orbital precession enhanced the northeastern monsoon. This pattern arises because during these two periods, a weakened southeastern monsoon reduced the amount of rainfall during the long rainy season and enhanced the opposing effect of evaporation intensity and/or length of the austral winter dry season. Importantly, our lake-based reconstruction of moisture-balance seasonality in equatorial East Africa also helps us understand the oxygen isotope record contained in Mount Kilimanjaro ice. Negative correlation between ice core delta(18)O and Lake Challa delta(18)O(diatom) implies that moisture balance is not the primary climate control on the long-term trend in ice core delta(18)O.
AB - Multiproxy analysis of a well-dated 25 ka lake sediment sequence from Lake Challa, on the eastern flank of Mount Kilimanjaro (East Africa), reveals the climatic controls that govern both the lake's paleohydrology and the climate-proxy record contained in the mountain's receding ice cap. The oxygen isotope record extracted from diatom silica (delta(18)O(diatom)) in Lake Challa sediments captured dry conditions during the last glacial period and a wet late-glacial transition to the Holocene interrupted by Younger Dryas drought. Further, it faithfully traced gradual weakening of the southeastern monsoon during the Holocene. Overall, delta(18)O(diatom) matches the branched isoprenoid tetraether (BIT) index of rainfall-induced soil runoff, except during 25-22 ka and the past 5 k.y. when insolation forcing due to orbital precession enhanced the northeastern monsoon. This pattern arises because during these two periods, a weakened southeastern monsoon reduced the amount of rainfall during the long rainy season and enhanced the opposing effect of evaporation intensity and/or length of the austral winter dry season. Importantly, our lake-based reconstruction of moisture-balance seasonality in equatorial East Africa also helps us understand the oxygen isotope record contained in Mount Kilimanjaro ice. Negative correlation between ice core delta(18)O and Lake Challa delta(18)O(diatom) implies that moisture balance is not the primary climate control on the long-term trend in ice core delta(18)O.
UR - http://www.scopus.com/inward/record.url?scp=80955159690&partnerID=8YFLogxK
U2 - 10.1130/G32419.1
DO - 10.1130/G32419.1
M3 - Journal article
VL - 39
SP - 1111
EP - 1114
JO - Geology
JF - Geology
SN - 1943-2682
IS - 12
ER -