9:17 AM - 9:32 AM
[U03-02] Reconstructing productivity history of the central Okhotsk Sea and North-East Russia during the Mid-Pleistocene Transition
★Invited Papers
Keywords:Mid-Pleistocene Transition, Sterol, Okhotsk Sea, Super-interglaical
Biological productivity, influenced by climate and environmental factors, plays a crucial role in climate feedback mechanisms and the global carbon cycle. This study aims to contribute data for understanding these interactions by analyzing six sterol compounds (beta-sitosterol, stigmasterol, campesterol, dinosterol, brassicasterol, and 24-methylene cholesterol) extracted from core MD01-2414 (53o11.77′ N, 149o34.80′ E) in the central Okhotsk Sea, spanning 1200-600 ka, using gas chromatography-mass spectrometer. These sterols, sourced from various environments, serve as proxies for reconstructing terrestrial and marine productivity in the central Okhotsk Sea and northeast Siberia.
Our findings reveal that sterol concentrations generally track global glacial/interglacial cycles during the 1200-600 ka period, with higher values in interglacial and lower values in glacial periods. X-ray fluorescence scans for Ba/Ti and total organic carbon/total nitrogen (TOC/TN) ratios suggest changes in marine and terrestrial sources, supporting the notion that biological productivity predominantly influences sedimentary sterols at this site, affirming their validity as productivity proxies.
Based on sterol fluxes, sea surface temperature records from the northwest Pacific, and sea ice proxies from the Bering Sea, we observed an extreme cold (failed) interglacial period, Marine Isotope Stage (MIS) 23, followed by continued cold conditions in MIS 22. Both terrestrial and marine ecosystems in the research region experienced considerable stress during this period. Previous studies propose that increased sea ice expansion during this time may have led to the formation of North Pacific Intermediate Water, suppressing upwelling and CO2 transport from bottom water to the surface and atmosphere.
Integration of sterol data with sea surface temperature records of the Okhotsk Sea and northwest Pacific, as well as pollen, temperature, and sedimentary facies data from Lake El’gygytgyn in the Far East Arctic Siberian region, indicates a warming event at the onset of MIS 32, peaking in late MIS 32. This warming precedes other records of the "super-interglacial" MIS 31 and aligns with the maximum values of boreal and austral summer insolation.
In summary, considerations of terrestrial detritus transportation and organic matter preservation confirm the utility of sedimentary sterols as productivity proxies. Our results suggest higher marine and land productivity during interglacial periods in the northwest Pacific and northeast Siberia. Furthermore, cooling events around 900 ka and a warming trend during the glacial period, MIS 32, are evident in both sterol data and previous research records.
Our findings reveal that sterol concentrations generally track global glacial/interglacial cycles during the 1200-600 ka period, with higher values in interglacial and lower values in glacial periods. X-ray fluorescence scans for Ba/Ti and total organic carbon/total nitrogen (TOC/TN) ratios suggest changes in marine and terrestrial sources, supporting the notion that biological productivity predominantly influences sedimentary sterols at this site, affirming their validity as productivity proxies.
Based on sterol fluxes, sea surface temperature records from the northwest Pacific, and sea ice proxies from the Bering Sea, we observed an extreme cold (failed) interglacial period, Marine Isotope Stage (MIS) 23, followed by continued cold conditions in MIS 22. Both terrestrial and marine ecosystems in the research region experienced considerable stress during this period. Previous studies propose that increased sea ice expansion during this time may have led to the formation of North Pacific Intermediate Water, suppressing upwelling and CO2 transport from bottom water to the surface and atmosphere.
Integration of sterol data with sea surface temperature records of the Okhotsk Sea and northwest Pacific, as well as pollen, temperature, and sedimentary facies data from Lake El’gygytgyn in the Far East Arctic Siberian region, indicates a warming event at the onset of MIS 32, peaking in late MIS 32. This warming precedes other records of the "super-interglacial" MIS 31 and aligns with the maximum values of boreal and austral summer insolation.
In summary, considerations of terrestrial detritus transportation and organic matter preservation confirm the utility of sedimentary sterols as productivity proxies. Our results suggest higher marine and land productivity during interglacial periods in the northwest Pacific and northeast Siberia. Furthermore, cooling events around 900 ka and a warming trend during the glacial period, MIS 32, are evident in both sterol data and previous research records.