In this setting, the Sr- isotope data do not vary in phase with these sedimentological cycles, but demonstrate a long trend of Sr isotope change. This sequence spans a couple of sedimentological cycles that potentially represent precession-forced lake level variation. Here, we present a first set of data from a middle Pleistocene stratigraphical sequence in the Suguta Valley, South of the Turkana Basin in the EARS.
Such lacustrine Sr- isotope changes are believed to be paced by orbital-forced insolation cyclicity, and interpreted to be the result of changing contribution of run-off from different sub-catchments of lake Turkana, as climate change shifted regional rainfall patterns. Joordens et al., 2011 van der Lubbe et al., submitted). This Sr isotope signal was captured in the lacustrine fossil record of the Turkana Basin, and can be a useful chemostratigraphic tool (e.g. Several studies into the Quaternary stratigraphic record of the Sr- isotope composition of paleolake Turkana in the East African Rift System (EARS) show how variation of climate left a signal of changing lacustrine Sr isotope values. Vonhof, Hubert Junginger, Annett Agmon, Nadav Trauth, Martin The potential for increased rates of sea level rise related to polar ice sheet decay should be considered as a potential naturalĮxploring the Middle Pleistocene Lake Suguta Sr- isotope Stratigraphic record Therefore any anthropogenic climate warming will accelerate the natural process toward reduction in polar ice sheets. 10 ka will continue for another 15 to 20 k.y. Current and marine isotope stage 11 Milankovitch forcing are very similar, suggesting that the present interglacial (Holocene) that began ca. Variations in Earth's orbit around the sun (Milankovitch cycles) are considered to be a primary external force driving glacial-interglacial cycles. Our results show a warm marine isotope stage 11 interglacial climate with sea level as high as or above modern sea level that lasted for 25 to 30 k.y. The increased sea level requires reduction in modern polar ice sheets and is consistent with the interpretation that the West Antarctic ice sheet and the Greenland ice sheet were absent or greatly reduced during marine isotope stage 11. Here we present microfossil and isotopic data from marine sediments of the Cariaco Basin supporting the interpretation that global sea level was 10-20 m higher than today during marine isotope stage 11.
Because of the implications for future sea level rise, additional study of the conflicting evidence for warmer conditions and higher sea level during marine isotope stage 11 is needed. Sea level may have been more than 20 m higher than today during a presumably very warm interglacial about 400 ka during marine isotope stage 11.
The sea-level projections assume that polar ice sheets will remain stable or even increase on time scales of centuries, but controversial geologic evidence suggests that current polar ice sheets have been eliminated or greatly reduced during previous Pleistocene interglacials indicating that modern polar ice sheets have become unstable within the natural range of interglacial climates. Sea level is projected to rise between 13 and 94 cm over the next 100 yr due to continued climate warming. Pleistocene reduction of polar ice caps: Evidence from Cariaco Basin marine sediments