Hokkaido University · Earth and Planetary Sciences
Professor Masanobu Yamamoto's research lab specializes in paleoceanography and paleoclimatology, focusing on reconstructing past climate dynamics in the North Pacific and Arctic Oceans using high-resolution marine sediment records. The lab investigates the variability of ocean currents, monsoon systems, and sea surface temperatures in response to orbital forcing and climate oscillations such as ENSO and the North Pacific Oscillation. Key research directions include understanding the mechanisms behind latitudinal shifts of oceanic fronts, the role of atmospheric circulation in glacial-interglacial transitions, and the long-term evolution of Arctic Ocean circulation. The lab employs alkenone-based sea surface temperature reconstructions and mineralogical proxies to decipher climate feedbacks and teleconnections across the Pacific basin.
Figures are computed from collected data and may differ slightly.
The late Quaternary records of alkenone sea surface temperature (SST) in the Japan and California margins showed orbital‐scale anti‐phase SST variations between the two margins. This east‐west seesaw‐like change agreed well with the long‐term El Niño‐Southern Oscillation (ENSO) behavior predicted by the Zebiak‐Cane ENSO model [ Clement et al. , 1999 ] as regards both the timing and frequency during 0–60 ka and 120–145 ka, and is attributed to the precession‐controlled change in tropical ENSO beh
We have generated a high‐resolution record of alkenone sea surface temperature (SST) between 10–24 ka from Core MD01‐2421 off central Japan, in the northwestern Pacific. The cooling by 5°C from 21 ka to 12.8 ka implies the equatorward shift of the subarctic boundary in the northwestern Pacific by ∼2.8° in latitude. This shift was a result of the stronger summer Okhotsk High. The Okhotsk High was likely enhanced by the combined effects of El Niño‐like conditions in the tropical Pacific and the he
Abstract. Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard–Oeschger (D–O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emi
Abstract We present a palaeoceanographic perspective of the North Pacific during the last two glacial cycles based on U‐derived palaeotemperature records of IMAGES Core MD01‐2421 off the coast of central Japan and cores from the Ocean Drilling Program (ODP) Sites 1014 and 1016 off the coast of California. The sea surface temperature (SST) differences between ODP Sites 1014 and 1016 (ΔSST northeastern Pacific (NEP) = SST ODP1014 – SST ODP1016 ) indicate the intensity of the California Current. Co
Abstract. The Beaufort Gyre (BG) and the Bering Strait inflow (BSI) are important elements of the Arctic Ocean circulation system and major controls on the distribution of Arctic sea ice. We report records of the quartz ∕ feldspar and chlorite ∕ illite ratios in three sediment cores from the northern Chukchi Sea, providing insights into the long-term dynamics of the BG circulation and the BSI during the Holocene. The quartz ∕ feldspar ratio, interpreted as a proxy of the BG strength, gradually d
Abstract. The response of the East Asian winter monsoon variability to orbital forcing is still unclear, and hypotheses are controversial. We present a 150 000 yr record of sea surface temperature difference (ΔSST) between the South China Sea and other Western Pacific Warm Pool regions as a proxy for the intensity of the Asian winter monsoon, because the winter cooling of the South China Sea is caused by the cooling of surface water at the northern margin and the southward advection of cooled wa
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