Plio‐Pleistocene Ocean Circulation Changes in the Gulf of Alaska and Its Impacts on the Carbon and Nitrogen Cycles and the Cordilleran Ice Sheet Development
Open Access
- 12 July 2022
- journal article
- research article
- Published by American Geophysical Union (AGU) in Paleoceanography and Paleoclimatology
- Vol. 37 (7)
Abstract
The modern Gulf of Alaska (GOA) is a Cordilleran Ice Sheet (CIS) region, estimated to be important for nutrient cycling and CO2 exchange. Little is known of the GOA evolution over the Pliocene and Pleistocene as well as its impact on the CIS development, when other evidence for changing North Pacific circulation has emerged. We analyzed Integrated Ocean Drilling Program Expedition 341 Site U1417 sediments, which extend through the Plio‐Pleistocene transition (4–1.7 Ma), focusing on productivity‐related biomarkers (alkenones, brassicasterol), siliceous microfossils and bulk carbon and nitrogen stable isotopes. Our results show two dominant water column regimes: one characterized by high silica and low organic matter (OM) preservation, containing microorganism remains from a mix of habitats (4–3.7 Ma) and a second characterized by low biogenic silica and increased OM preservation of microorganisms from dominantly open ocean habitats (3.33–3.32 Ma and 2.8–1.66 Ma). An increase of phytoplankton diversity (3.7–3.35 Ma, 3.19–2.82 Ma) characterizes the two transitions of water column conditions, from oxygenated to reductive, that we attribute to a change from ocean mixing to strong stratified conditions with some occasional mixing. The biogeochemical changes in the GOA follow 400 and 100 kyr eccentricity cycles which are also reflected in changes in the CIS. We conclude that the CIS expansion created high nutrient low chlorophyll conditions in the GOA during the Mid Piacenzian Warm Period and the early Pleistocene. In turn, positive feedbacks increased marine productivity export, atmospheric CO2 drawdown and further CIS expansion.Keywords
Funding Information
- Helmholtz Association (VH‐NG‐1101)
This publication has 110 references indexed in Scilit:
- Nutrient leakage from the North Pacific to the Bering Sea (IODP Site U1341) following the onset of Northern Hemispheric Glaciation?Paleoceanography and Paleoclimatology, 2013
- High interglacial diatom paleoproductivity in the westernmost Indo‐Pacific Warm Pool during the past 130,000 yearsPaleoceanography and Paleoclimatology, 2012
- Glacial flour dust storms in the Gulf of Alaska: Hydrologic and meteorological controls and their importance as a source of bioavailable ironGeophysical Research Letters, 2011
- A biophysical NPZ model with iron for the Gulf of Alaska: Reproducing the differences between an oceanic HNLC ecosystem and a classical northern temperate shelf ecosystemDeep Sea Research Part II: Topical Studies in Oceanography, 2009
- Paleoceanography of the Gulf of Alaska during the past 15,000 years: Results from diatoms, silicoflagellates, and geochemistryMarine Micropaleontology, 2009
- High‐amplitude variations in North Atlantic sea surface temperature during the early Pliocene warm periodPaleoceanography and Paleoclimatology, 2009
- The uptake and export of silicon and nitrogen in HNLC waters of the NE Pacific OceanDeep Sea Research Part II: Topical Studies in Oceanography, 2005
- Lipid biomarker fluxes in the Arabian Sea, with a comparison to the equatorial Pacific OceanDeep Sea Research Part II: Topical Studies in Oceanography, 2002
- Review of alkenone calibrations (culture, water column, and sediments)Geochemistry, Geophysics, Geosystems, 2001
- The Occurrence of Brassicasterol in the Diatoms, Cyclotella nana and Nitzschia closteriumNIPPON SUISAN GAKKAISHI, 1971