Pleistocene water cycle and eastern boundary current processes along the California continental margin

Abstract

1] Coastal marine sediments contain mixtures of terrestrial and marine paleoclimate proxies that record how the coastal water cycle has behaved over long time frames. We explore a 600 kyr marine record from ODP Site 1018, located due west of Santa Cruz, California, to identify coastal wet and dry periods and to associate them with oceanographic processes. Wet periods in central California, identified by increased tree pollen relative to pollen from grasslands and scrublands, are found on every major deglaciation in the last 600 kyr. Sea surface temperature (SST) data were collected for the last two deglaciations. Wet periods are associated with a rapid rise in SST off central California. SST gradients along the California margin and changes in biogenic deposition show that wet periods in central California are associated with a weakening of the California Current and weakened coastal upwelling. High carbonate production suggests that there was significant curl-of-wind stress upwelling offshore. We propose that wet periods in central California are associated with a meteorological connection to the tropical Pacific and weakened southward flow in the California Current that shunted temperate Pacific water northward into the Alaska gyre. We do not observe evidence for a south-shifted westerly storm track at the last glacial maximum but find that wet periods are diachronous along the California margin. The wettest period around the Santa Barbara Basin peaked at 16 ka, preceding the wet peak in central and northern California by 4 kyr.Citation: Lyle, M., L. Heusser, C. Ravelo, D. Andreasen, A. Olivarez Lyle, and N. Diffenbaugh (2010), Pleistocene water cycle and eastern boundary current processes along the California continental margin, Paleoceanography, 25, PA4211,

Fluvial tufa evidence of Late Pleistocene wet intervals from Santa Barbara, California, U.S.A.

“…This data matches well with an extended wet interval observed from Moaning Cave on the western foothills of the Sierra Nevada that lasted from about 12.4 ka to about 9.6 ka (Oster et al, 2009). Further, the occurrence of a peak wet event off the coast near the California-Oregon border at ODP site 1019 based on Alnus (alder) pollen (Lyle et al, 2010(Lyle et al, , 2012 also coincides with our tufa record. Thus far, comparisons between pollen records in northern and southern California suggest that southern California experienced a peak wet event approximately 5 ka earlier than central and northern coastal California, where maximum wet conditions occurred between 12.5 and 4.5 ka in central California and between 17.4 and 14.2 ka in southern California (Lyle et al, 2010;Lyle et al, 2012).…”

“…Further, the occurrence of a peak wet event off the coast near the California-Oregon border at ODP site 1019 based on Alnus (alder) pollen (Lyle et al, 2010(Lyle et al, , 2012 also coincides with our tufa record. Thus far, comparisons between pollen records in northern and southern California suggest that southern California experienced a peak wet event approximately 5 ka earlier than central and northern coastal California, where maximum wet conditions occurred between 12.5 and 4.5 ka in central California and between 17.4 and 14.2 ka in southern California (Lyle et al, 2010;Lyle et al, 2012). In contrast, our new tufa record indicates that coastal southern California remained substantially wet at 11.9 ± 1.5 ka thus potentially coinciding with wet events north of our site, and challenging the time-transient wet event proposed by Lyle et al, 2012 that suggests wet periods in southern and northern California were diachronous across the deglacial.…”

“…Detailed analyses of those proxy records with high temporal resolution and improved dating precision have revealed that temperature and hydroclimate were spatially and temporally variable across the western US in the late glacial and across the deglacial (Lyle et al, 2012;Kirby et al, 2013). In particular, pollen records from marine sediments offshore southern and northern California (ODP site 893 and 1019, respectively) reveal variable timing of hydroclimatic change along the coast (Lyle et al, 2010(Lyle et al, , 2012. Adding records that concentrate on spatial and temporal hydroclimate patterns is key to resolve the history and causes of hydroclimatic variability for specific regions across the western US (e.g., coastal versus inland).…”

Sea-level driven glacial-age refugia and post-glacial mixing on subtropical coasts, a palaeohabitat and genetic study

“…The cold California Current, upwelling, and upwelling-induced low clouds and fog along the Pacific coast limit seasonal and latitudinal temperature change relative to, for instance, the Atlantic coast [53], and limit temperature excursions in coastal estuary settings. In addition, in the northern part of our study region, sea-surface temperatures appear to have increased by only 2.78C between LGM and present [54], which is similar to or less than temperature changes produced by modern El Niñ o events [55]. Temperature differences in Pacific coast estuaries are also strongly influenced by estuary type and residence time [56].…”

Demographic history of Heermann's Gull (Larus heermanni) from late Quaternary to present: Effects of past climate change in the Gulf of California

“…During the late Pleistocene, the North Pacific developed into a cold, rocky shore ecosystem that provided complex and productive environments for many marine species, and dynamic ocean currents and upwelling that led to higher plankton productivity (Paine 2002, Graham et al 2003, Lyle et al 2010. Coastal areas in the North Pacific are highly variable environments, where changes in current patterns, ocean circulation, and upwelling have reversed in different time scales, ranging from 10,000 to 100,000 yr BP (Kennett and Ingram 1995, Kiefer et al 2001, Hewitt 2004, affecting productivity (Webb and Bartlein 1992).…”