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Paleoproductivity and Stratification Across the Subarctic Pacific Over Glacial-Interglacial Cycles

机译：在冰川层峡循环上占亚宫太平洋地区的古粪便和分层

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In the Subarctic Pacific, variability in productivity on glacial-interglacial timescales is often attributed to changes in stratification and nutrient delivery to the surface, but the mechanisms driving this relationship are poorly constrained. Records extending beyond the last glacial maximum from both the open ocean and the marginal seas are required to investigate the timing and magnitude of different influential processes through the full glacial cycle. In this study we generated ~(231)Pa/~(230)Th over 210,000 years in order to capture two full glacial cycles of paleoproductivity on the Juan de Fuca Ridge in the East Subarctic Pacific. The sedimentary ~(231)Pa/~(230)Th ratios are always equal to or greater than the seawater production ratio (0.093), consistent with enhanced biological scavenging in this region. The temporal pattern of ~(231)Pa/~(230)Th burial is remarkably coherent with changes in climate, with high values (0.20) during peak interglacial periods descending to low values (0.10) during peak glacial conditions, consistent with other long productivity records from this region. We investigate the possible contributions of temperature, sea ice formation, Bering Strait closure, wind strength, upwelling, and subsurface nutrient concentrations as possible mechanisms by which physical and/or chemical stratification emerged during glacial periods. Due to the low sea surface salinity in the North Pacific, cooling actually weakens the density gradient in surface (0-200 m) waters. To create the steep density profiles that characterize physical stratification, additional processes to reduce the salinity of surface waters must occur during glacial periods. We suggest that regional sea ice formation and Bering Strait closure may have contributed to freshening surface waters and enhancing physical stratification during glacial periods. Additionally, simulated weak winds in this region due to the southward shift of the glacial westerlies may have further reduced s
机译：在亚奇奇太平洋地区，冰川间间时间尺度的生产率的可变性通常归因于地面的分层和营养输送的变化，但驱动这种关系的机制受到严重受损。需要超出开放海洋和边缘海域最后最后冰川最大值的记录，以研究通过完全冰川周期的不同影响流程的时序和程度。在这项研究中，我们生成了〜（231）PA /〜（230）TH超过21万年，以捕获东亚曲率太平洋的Juan de Fuca山脊上的两个完全冰川山脉。沉积〜（231）PA /〜（230）速率始终等于或大于海水生产比（0.093），这与该地区的增强生物清除一致。 〜（231）PA /〜（230）的时间图案在气候变化中显着相干，高值（0.20）在峰值冰川条件下降低到低值（0.10），与其他长期一致来自该地区的生产力记录。我们调查温度，海冰形成，白冰封闭，风力强度，升值和地下营养浓度的可能贡献，以及在冰川期间出现的物理和/或化学分层。由于北太平洋的海面盐度低，冷却实际上削弱了表面（0-200米）水处的密度梯度。为了创建特征物理分层的陡粒密度曲线，必须在冰川期间发生额外的减少表面水域盐度的过程。我们建议区域海冰形成和白血动海峡关闭可能导致新鲜表面水域，并在冰川期间提高物理分层。另外，由于冰川港口的南向偏移，该区域的模拟弱风可能进一步减少

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