What induced long-term Hg enrichment in interglacial sediments during the Cryogenian
0
Citation
73
Reference
10
Related Paper
Abstract. The role of nutrients and their impact on primary productivity and the fluctuations in atmospheric CO2 over glacial-interglacial periods are intensely debated. One of the cornerstones is the role of phosphorus (P; in the form of phosphate). Suggestions as to the importance of P evolved from an earlier proposal that P actively participated in changing productivity rates and therefore climate change, to the most recent one that changes in the glacial ocean inventory of phosphorus were small and not influential if compared to other macronutrients, such as nitrogen. Using new data coming from a selection of ODP sites, we illustrate oceanic P sedimentary phases distribution and reactive P burial fluxes, and we show how P burial fluxes changed over the last glacial-interglacial period. Concentrations of reactive P are generally lower during glacial times, while mass accumulation rates (MAR) show higher variability. On a global scale, glacial burial fluxes of reactive P are lower than those during interglacial periods by 7–10%, because lack of burial of reactive P on the glacial reduced shelf was apparently not compensated by burial in other regions of the ocean. Using the calculated changes in P burial, we try to infer their possible impact on the phosphate inventory in the world oceans. Using a simple mathematical approach, we find that these changes alone could have increased the phosphate inventory of glacial ocean waters by 20–40% compared to interglacial stages. Variations in the C/P reactive ratios and in the P sedimentary phases distribution at the investigated sites seem to indicate that at the onset of interglacial stages, shallower sites experienced an increase in reactive P concentrations. This seems to point to P-richer waters at glacial terminations, supporting the shelf-nutrient hypothesis and giving phosphorus a role as a potential player in climate change.
Cite
Citations (1)
Confusion
Cite
Citations (0)
Enhanced ocean stratification during glacial periods is the main factor depressing the biogenic opal productivity in the subarctic North Pacific and its marginal seas. However, there are no quantitative estimations of glacial nutrient reduction despite the importance of the glacial-interglacial nutrient cycle. In this study, δ30Si of diatom frustules (δ30Sidiatom) was measured in order to provide a record of silicic acid utilization over the last 600 ka at IODP Site U1343. The δ30Sidiatom record revealed distinct orbital-scale changes: high δ30Sidiatom (i.e., high silicic acid utilization) during the interglacial periods and low δ30Sidiatom (i.e., low silicic acid utilization) during the glacial periods. These changes are explained by the glacial-interglacial differences of Fe-concentration and sea-ice influence on surface-water productivity. This study estimated the glacial reduction of silicic acid supply and utilization in the Bering slope area. Based on the glacial-interglacial average δ30Sidiatom values using the Rayleigh closed model, the glacial silicic acid level was estimated to be >63% of the interglacial level and the glacial silicic acid utilization was significantly lower (<37%) than during interglacial periods (~64%).
Silicic acid
Silicic
Subarctic climate
Cite
Citations (5)
Ice core
Cite
Citations (56)
Cite
Citations (51)
This chapter contains sections titled: Introduction Onset of Northern Hemisphere Glaciation. Glacial-Interglacial Cycles The Mid-Pleistocene Revolution Rapid Climate Changes in Glacial Periods Rapid Climatic Changes During the Last Glacial-Interglacial Transition Rapid Climate Changes within Interglacials The Future Appendix I: Orbital Forcing; the Basics [Adapted from Wilson Et Al, 2000 and Lowe and Walker, 2000]
Orbital forcing
Milankovitch cycles
Climate state
Cite
Citations (51)
Abstract. The role of nutrients, such as phosphorus (P), and their impact on primary productivity and the fluctuations in atmospheric CO2 over glacial-interglacial periods are intensely debated. Suggestions as to the importance of P evolved from an earlier proposal that P actively participated in changing productivity rates and therefore climate change, to most recent ones that changes in the glacial ocean inventory of phosphorus were important but not influential if compared to other macronutrients, such as nitrate. Using new data coming from a selection of ODP sites, we analyzed the distribution of oceanic P sedimentary phases and calculate reactive P burial fluxes, and we show how P burial fluxes changed over the last glacial-interglacial period at these sites. Concentrations of reactive P are generally lower during glacial times, while mass accumulation rates (MAR) of reactive P show higher variability. If we extrapolate for the analyzed sites, we may assume that in general glacial burial fluxes of reactive P are lower than those during interglacial periods by about 8%, because the lack of burial of reactive P on the glacial shelf reduced in size, was apparently not compensated by burial in other regions of the ocean. Using the calculated changes in P burial, we evaluate their possible impact on the phosphate inventory in the world oceans. Using a simple mathematical approach, we find that these changes alone could have increased the phosphate inventory of glacial ocean waters by 17–40% compared to interglacial stages. Variations in the distribution of sedimentary P phases at the investigated sites seem to indicate that at the onset of interglacial stages, shallower sites experienced an increase in reactive P concentrations, which seems to point to P-richer waters at glacial terminations. All these findings would support the Shelf-Nutrient Hypothesis, which assumes that during glacial low stands nutrients are transferred from shallow sites to deep sea with possible feedback on the carbon cycle.
Cite
Citations (32)
THE features of the Glacial deposits and associated phenomena just discussed are in general so clear that most observers would arrive at the same conclusion regarding them, but there are some other features about which, either due to their controversial nature or the conflicting character of the evidence, there is not yet such general agreement. These are ( a ) the evidence for interglacial Periods in the Drift of these counties, ( b ) the raised beaches of East Durham, ( c ) the origin of the leafy clays, ( d ) the explanation of the distribution of fragments of certain rocks —Flint, Chalk, Magnesian Limestone—in the Superficial Deposits.
Sequence (biology)
Cite
Citations (11)
This chapter contains sections titled: Introduction: Using the Past to Constrain the Future The Glacial-Interglacial CO2 Problem How It Works: A Hitchhiker's Guide to the Marine Carbon Cycle Help From Ocean Muds: Paleoceanographic Proxies What Caused the 70- to 90-ppm Glacial-to -Interglacial Change in Atmospheric CO2? Summary and Outlook
Deglaciation
Cite
Citations (141)