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An interhemispheric hydrologic seesaw--in which latitudinal migrations of the Intertropical Convergence Zone (ITCZ) produce simultaneous wetting (increased precipitation) in one hemisphere and drying in the other--has been discovered in some tropical and subtropical regions (1-3). For instance, Chinese and Brazilian subtropical speleothem (cave formations such as stalactites and stalagmites) records show opposite trends in time series of oxygen isotopes (a proxy for precipitation variability) at millennial to orbital timescales (2,3), suggesting that hydrologic cycles were antiphased in the northerly versus southerly subtropics. This tropical to subtropical hydrologic phenomenon is likely to be an initial and important climatic response to orbital forcing (3). The impacts of such an interhemispheric hydrologic seesaw on higher-latitude regions and the global climate system, however, are unknown. Here we show that the antiphasing seen in the tropical records is also present in both hemispheres of the mid-latitude western Pacific Ocean. Our results are based on a new 550,000-year record of the growth frequency of speleothems from the Korean peninsula, which we compare to Southern Hemisphere equivalents (4). The Korean data are discontinuous and derived from 24 separate speleothems, but still allow the identification of periods of peak speleothem growth and, thus, precipitation. The clear hemispheric antiphasing indicates that the sphere of influence of the interhemispheric hydrologic seesaw over the past 550,000 years extended at least to the mid-latitudes, such as northeast Asia, and that orbital-timescale ITCZ shifts can have serious effects on temperate climate systems. Furthermore, our result implies that insolation driven ITCZ dynamics may provoke water vapour and vegetation feedbacks in northern mid-latitude regions and could have regulated global climate conditions throughout the late Quaternary ice age cycles., (6) The Korean peninsula in northeast Asia is situated on the boundary between the world's largest continent and largest ocean (5) and has a typical mid-latitude climate that is strongly [...]

Understanding Oligocene paleoceanographic changes is helpful for preparing the global warming in the future because the levels of atmospheric pCO2 in the Oligocene were similar to those expected within the next century. However, the overall paleoclimatic and paleoceanographic history of the Oligocene still remain unclear even though our knowledge and technic have been improved by previous researches. In this study, we newly compiled Cibicidoides spp. δ18O records from global oceanic basin for the more reasonable assessment of the paleoceanographic changes during the Oligocene. We divided this Oligocene δ18O profile into five phases: an abrupt increase in δ18O values during the Eocene-Oligocene transition (EOT) (Phase 1), a gradual decrease in the early Oligocene (Phase 2), a long-term increase in the early to middle Oligocene (Phase 3), a gradual decrease in the late Oligocene (Phase 4) and an abrupt increase near the Oligocene– Miocene transition (OMT) (Phase 5). This Oligocene see-saw in the global scale δ18O profile is not likely to be directly connected to the strengthening and stratification of oceanic circulation related to the unidirectional strengthening of the Antarctic circumpolar current (ACC) and the North Atlantic Deep Water (NADW). Alternatively, we suggest that the invigorated oceanic circulation contributed to the interbasinal differences in δ18O values. For a more definite interpretation on the long-term δ18O changes during the Oligocene, future works will require the reconstruction of higher resolution and more reproducible data recording the changes of Antarctic ice sheets and atmospheric pCO2 as well as information about the tectonic and paleoceanographic history. [ABSTRACT FROM AUTHOR]

Competing Interests: Competing interests statement:The author declares no competing interest.