North Pacific Paleotemperature and Paleoproductivity Reconstructions Based on Diatom Species

Abstract

Regionally developed diatom‐based transfer functions reconstruct both summer sea surface temperature and primary productivity (PP) in the North Pacific based on a calibration data set including the eastern subtropical gyre (California and Oregon), the Gulf of Alaska, the western Pacific, and Bering Sea. Factors of the floral assemblage and environment data sets, and canonical correspondence, support estimation of two essentially orthogonal variables. Validation of the summer sea surface temperature transfer function resulted in r2jack of 0.9 and a root‐mean‐square error of prediction of 1.0°C over a range of 7–17°C. The summer PP transfer function yielded r2jack of 0.7 and a root‐mean‐square error of prediction of 219 g C·m2·year over a range of 200–2,000 g C·m2·year. Application in downcore locations within the modern nearshore upwelling regime and within the California Current offshore Oregon reveals that during Holocene time higher PP (>800 g C·m2·year) was associated with cooler temperatures (<16°C) forced by upwelling. In contrast, during the Last Glacial Maximum, when subpolar conditions are present off Oregon, higher PP (>1,000 g C·m2·year) was associated with warmer SSTs (>10°C; significant in the nearshore site). This finding supports previous hypotheses that in cold regimes warming may augment biological production, perhaps by relieving metabolic constraints. This is of particular interest because of projected amplification of future warming in high latitudes and the potential for greening of the subpolar and polar oceans.

Sediment controls dynamic behavior of a Cordilleran Ice Stream at the Last Glacial Maximum

“…E. pacifica and U. peregrina are indicators of suboxic conditions along the Northeastern Pacific margin 36 and reduced oxygen may be a factor leading to decreased diversity; however, both the lack of laminations and other low oxygen benthic taxa ( Supplementary Fig. 6 37,38 . Sea-ice diatoms decrease in abundance throughout Facies III ( Fig.…”

Sea Surface Temperature Changes Reflected by Diatoms in the P6-10 Core from 1893 to 2013 from Prydz Bay, Antarctica

“…Therefore, diatoms can reflect the past environment [5] as an effective bioenvironmental proxy indicator and have important advantages in the research of climate and environmental reconstruction. Benefitting from the development of dating technology and core drilling technology [6,7], reconstruction of the palaeo-climate and the palaeo-environment based on diatoms has been widely used in lakes [8][9][10] and oceans [11][12][13] all over the world. In the lakes, the research includes water depth [14], salinity [15], pH [16], conductivity [17], and indicators such as nitrogen and phosphorus that reflect eutrophication [18][19][20].…”

Middle to Late Holocene Sea Surface Temperature and Productivity Changes in the Northeast Pacific

“…The primary productivity patterns observed, mechanisms proposed to explain those changes, and the implications of these changes are also contentious. In particular, the primary productivity records analyzed in those studies are dependent on spatial calibration with modern observations (Lopes & Mix, 2018; Ren et al., 2014) or are subject to sediment dilution (Gardner et al., 1997) and diagenesis (Ragueneau et al., 2000). Although the proposed mechanism to explain observed primary productivity changes, upwelling season length, is supported by simulations from an atmospheric regional model (Diffenbaugh & Ashfaq, 2007), it is unclear whether changes driven by this mechanism are detectable in proxy records.…”