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Enhanced subarctic Pacific stratification and nutrient utilization during glacials over the last 1.2 Myr
Author(s) -
Knudson Karla P.,
Ravelo Ana Christina
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl066317
Subject(s) - subarctic climate , iron fertilization , glacial period , oceanography , interglacial , geology , environmental science , stratification (seeds) , nutrient , biogeochemical cycle , earth science , phytoplankton , ecology , paleontology , biology , seed dormancy , botany , germination , dormancy
The relationship between climate, biological productivity, and nutrient flux is of considerable interest in the subarctic Pacific, which represents an important high‐nitrate, low‐chlorophyll region. While previous studies suggest that changes in iron supply and/or physical ocean stratification could hypothetically explain orbital‐scale fluctuations in subarctic Pacific nutrient utilization and productivity, previous records of nutrient utilization are too short to evaluate these relationships over many glacial‐interglacial cycles. We present new, high‐resolution records of sedimentary δ 15 N, which offer the first opportunity to evaluate systematic, orbital‐scale variations in subarctic Pacific nitrate utilization from 1.2 Ma. Nitrate utilization was enhanced during all glacials, varied with orbital‐scale periodicity since the mid‐Pleistocene transition, was strongly correlated with enhanced aeolian dust and low atmospheric CO 2 , but was not correlated with productivity. These results suggest that glacial stratification, rather than iron fertilization, systematically exerted an important regional control on nutrient utilization and air‐sea carbon flux.