%0 Journal Article %1 2003AGUFMOS31B0208B %A Barron, J. A. %A Heusser, L. %D 2003 %J AGU Fall Meeting Abstracts %K Abies_grandis California Calocedrus_decurrens Central_Gyre Dark_Ages_Cold_period Douglas_fir Eel_River Fir Holocene Little_Ice_Age Medieval_Warm_period North_Coast_Range Pinus_ponderosa Ponderosa_pine Pseudoeunotia_doliolus Pseudotsuga_menziesii Quercus_chrysolepis Subtropical_High bog climate coast diatom hard-leaf_oak incense_cedar paleoclimate pollen proxy transect %P B208+ %T A High Resolution Climatic Transect Across the Coastal Margin of Northernmost California During the Past 3,500 Years %X A diatom proxy for SST from two offshore cores, ODP 1019 (41.7 deg. N, 124.9 deg. W, 980 m water depth) and TN062 0550 (40.9 deg. N,124.6 deg. W, 570 m water depth), and a pollen proxy for summer moisture from terrestrial bog core SB70-1 (40.3 deg. N, 123.4 deg. W, 910 m altitude), together reveal a detailed record of climate change in the Eel River basin area of northernmost California during the past 3,500 years. Age models for all three cores are well constrained by AMS dates, with sample spacing varying from ca. 150 years at ODP 1019 to between 30 and 50 years in both TN062 0550 and SB70-1. As indicated by the diatom proxy for the warm waters of the Central Gyre, Pseudoeunotia doliolus, a late Holocene trend toward warmer fall SST's began approximately 1,000 years earlier at the more offshore (60 km offshore) ODP Site 1019 (ca. 3.4 ka), than it did in the more coastal (33 km offshore) piston core TN062 0550 (ca. 2.4 ka). This diatom proxy suggests that a pronounced offshore-coastal SST gradient existed during the fall between the two sites until ca. 1.4 ka (or AD 600), when this climatic gradient abruptly collapsed. During the past 1,400 years, diatom data at both sites argue for cooling of SST's between ca. AD 600 and AD 900, followed by pronounced warming between ca. AD 950 and AD 1200, and then followed by cooling between ca. AD 1350 and AD 1800. The ages of these intervals are suggestive of local expression of the Dark Ages Cold period, Medieval Warm period, and the Little Ice Age. Pollen in the core SB70-1 is derived from the local montane communities of mixed evergreen forest, forests that are dominated by Douglas fir (Pseudotsuga menziesii), and include hard-leafed oaks (Quercus chrysolepis), as well as incense cedar (Calocedrus decurrens), Ponderosa pine (Pinus ponderosa), and fir (Abies grandis). We interpret increased oak, which is associated with increased herbs, as indicative of warm dry conditions, whereas increased Douglas fir would suggest a more closed forest with increased summer moisture. Prior to ca. AD 500 AD, oak pollen dominates over Douglas fir pollen, suggesting that comparatively warm, dry summers prevailed in the North Coast Range. Between ca. AD 500 and AD 600, Douglas fir pollen increased from roughly 15% to nearly 40% of the pollen assemblage, evidence of an abrupt increase in summer moisture that was coincident with the collapse in the offshore-coastal climatic gradient suggested by diatoms. Presumably, regional cooling between AD 600 and AD 500 may have shifted the summer position of the Subtropical High further to the south, causing changes in both the diatom and pollen proxies. After ca. AD 600, fluctuations in the relative percentages of Douglas fir and oak pollen compare well with the generalized climate trends suggested by the diatoms in the offshore cores.

@article{2003AGUFMOS31B0208B, abstract = {A diatom proxy for SST from two offshore cores, ODP 1019 (41.7 deg. N, 124.9 deg. W, 980 m water depth) and TN062 0550 (40.9 deg. N,124.6 deg. W, 570 m water depth), and a pollen proxy for summer moisture from terrestrial bog core SB70-1 (40.3 deg. N, 123.4 deg. W, 910 m altitude), together reveal a detailed record of climate change in the Eel River basin area of northernmost California during the past 3,500 years. Age models for all three cores are well constrained by AMS dates, with sample spacing varying from ca. 150 years at ODP 1019 to between 30 and 50 years in both TN062 0550 and SB70-1. As indicated by the diatom proxy for the warm waters of the Central Gyre, Pseudoeunotia doliolus, a late Holocene trend toward warmer fall SST's began approximately 1,000 years earlier at the more offshore (60 km offshore) ODP Site 1019 (ca. 3.4 ka), than it did in the more coastal (33 km offshore) piston core TN062 0550 (ca. 2.4 ka). This diatom proxy suggests that a pronounced offshore-coastal SST gradient existed during the fall between the two sites until ca. 1.4 ka (or AD 600), when this climatic gradient abruptly collapsed. During the past 1,400 years, diatom data at both sites argue for cooling of SST's between ca. AD 600 and AD 900, followed by pronounced warming between ca. AD 950 and AD 1200, and then followed by cooling between ca. AD 1350 and AD 1800. The ages of these intervals are suggestive of local expression of the Dark Ages Cold period, Medieval Warm period, and the Little Ice Age. Pollen in the core SB70-1 is derived from the local montane communities of mixed evergreen forest, forests that are dominated by Douglas fir (Pseudotsuga menziesii), and include hard-leafed oaks (Quercus chrysolepis), as well as incense cedar (Calocedrus decurrens), Ponderosa pine (Pinus ponderosa), and fir (Abies grandis). We interpret increased oak, which is associated with increased herbs, as indicative of warm dry conditions, whereas increased Douglas fir would suggest a more closed forest with increased summer moisture. Prior to ca. AD 500 AD, oak pollen dominates over Douglas fir pollen, suggesting that comparatively warm, dry summers prevailed in the North Coast Range. Between ca. AD 500 and AD 600, Douglas fir pollen increased from roughly 15% to nearly 40% of the pollen assemblage, evidence of an abrupt increase in summer moisture that was coincident with the collapse in the offshore-coastal climatic gradient suggested by diatoms. Presumably, regional cooling between AD 600 and AD 500 may have shifted the summer position of the Subtropical High further to the south, causing changes in both the diatom and pollen proxies. After ca. AD 600, fluctuations in the relative percentages of Douglas fir and oak pollen compare well with the generalized climate trends suggested by the diatoms in the offshore cores.}, added-at = {2008-05-17T02:13:28.000+0200}, adsnote = {Provided by the SAO/NASA Astrophysics Data System}, adsurl = {http://adsabs.harvard.edu/abs/2003AGUFMOS31B0208B}, author = {{Barron}, J. A. and {Heusser}, L.}, biburl = {https://www.bibsonomy.org/bibtex/2fcb08fb43a49ffd0c3694eaaa8fde437/thulefoth}, description = {A High Resolution Climatic Transect Across the Coastal Margin of Northernmost Ca}, interhash = {abcf75d9dc923d6e26c7764c67a562ae}, intrahash = {fcb08fb43a49ffd0c3694eaaa8fde437}, journal = {AGU Fall Meeting Abstracts}, keywords = {Abies_grandis California Calocedrus_decurrens Central_Gyre Dark_Ages_Cold_period Douglas_fir Eel_River Fir Holocene Little_Ice_Age Medieval_Warm_period North_Coast_Range Pinus_ponderosa Ponderosa_pine Pseudoeunotia_doliolus Pseudotsuga_menziesii Quercus_chrysolepis Subtropical_High bog climate coast diatom hard-leaf_oak incense_cedar paleoclimate pollen proxy transect}, month = {December}, pages = {B208+}, timestamp = {2008-05-17T02:13:28.000+0200}, title = {{A High Resolution Climatic Transect Across the Coastal Margin of Northernmost California During the Past 3,500 Years}}, year = 2003 }