scholarly journals Erratum: Corrigendum: Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs

2016 ◽  
Vol 9 (9) ◽  
pp. 728-728
Author(s):  
Luis P. A. M. Duprat ◽  
Grant R. Bigg ◽  
David J. Wilton
Keyword(s):  
Southern Ocean ◽  
Marine Productivity

scholarly journals Pyrogenic iron: The missing link to high iron solubility in aerosols

2019 ◽  
Vol 5 (5) ◽  
pp. eaau7671 ◽  
Author(s):  
Akinori Ito ◽  
Stelios Myriokefalitakis ◽  
Maria Kanakidou ◽  
Natalie M. Mahowald ◽  
Rachel A. Scanza ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Southern Ocean ◽  
Atmospheric Deposition ◽  
Field Data ◽  
Biological Productivity ◽  
Iron Solubility ◽  
Field Campaigns ◽  
Anthropogenic Perturbations ◽  
Marine Productivity ◽  
Multiple Field

Atmospheric deposition is a source of potentially bioavailable iron (Fe) and thus can partially control biological productivity in large parts of the ocean. However, the explanation of observed high aerosol Fe solubility compared to that in soil particles is still controversial, as several hypotheses have been proposed to explain this observation. Here, a statistical analysis of aerosol Fe solubility estimated from four models and observations compiled from multiple field campaigns suggests that pyrogenic aerosols are the main sources of aerosols with high Fe solubility at low concentration. Additionally, we find that field data over the Southern Ocean display a much wider range in aerosol Fe solubility compared to the models, which indicate an underestimation of labile Fe concentrations by a factor of 15. These findings suggest that pyrogenic Fe-containing aerosols are important sources of atmospheric bioavailable Fe to the open ocean and crucial for predicting anthropogenic perturbations to marine productivity.

scholarly journals East Antarctic Ice Sheet and Southern Ocean Response to Orbital Forcing from Late Miocene to Early Pliocene, Wilkes Land, East Antarctica

2021 ◽  
Author(s):  
◽  
Nikita Anne Turton
Keyword(s):  
Southern Ocean ◽  
Late Miocene ◽  
Ice Sheet ◽  
Orbital Forcing ◽  
Sea Ice Extent ◽  
Antarctic Ice Sheet ◽  
Early Pliocene ◽  
Wilkes Land ◽  
Marine Productivity ◽  
East Antarctic Ice Sheet

<p>Geological and ice sheet models indicate that marine-based sectors of the East Antarctic Ice Sheet (EAIS) were unstable during periods of moderate climatic warmth in the past. While geological records from the Middle to Late Pliocene indicate a dynamic ice sheet, records of ice sheet variability from the comparatively warmer Late Miocene to Early Pliocene are sparse, and there are few direct records of Antarctic ice sheet variability during this time period. Sediment recovered in Integrated Ocean Drilling Program U1361 drill core from the Wilkes Land margin provides a distal but continuous glacially-influenced record of the behaviour of Antarctic Ice Sheets.  This thesis presents marine sedimentological and x-ray fluorescence geochemical datasets in order to assess changes in the dynamic response of the EAIS and Southern Ocean productivity in the Wilkes Land sector during Late Miocene and Early Pliocene to climatic warming and orbital forcing between 6.2 and 4.4 Ma. Two primary lithofacies are identified which can be directly related to glacial–interglacial cycles; enhanced sedimentation during glacials is represented by low-density turbidity flows that occurred in unison with low marine productivity and reduced iceberg rafted debris. Interglacial sediments contain diatomaceous muds with short-lived, large fluxes of iceberg rafted debris preceding a more prolonged phase of enhanced marine productivity. Interglacial sediments coincide with a more mafic source of terrigenous sediment, interfered to be associated with an inland retreat of the ice margin resulting in erosion of lithologies that are currently located beneath the grounded EAIS. Poleward invigoration of the Antarctic Circumpolar Current during glacial–interglacial transitions is proposed to have intensified upwelling, enhancing nutrient availability for marine productivity, and increasing oceanic heat flux at the ice margin acting to erode marine ice sheet grounding lines and triggering retreat.  Spectral analysis of the datasets indicated orbital frequencies are present in the iceberg rafted debris mass accumulation rates at all three Milankovitch frequencies, with a dominant 100 kyr eccentricity driven ice discharge. Prolonged intervals of marine productivity correlate to 100 kyr cyclicity occurring at peaks in obliquity. The response of both ice sheet and biological systems to 100 kyr cyclicity may indicate eccentricity-modulated sea ice extent controls the influx of warm water onto the continental shelf.</p>

scholarly journals East Antarctic Ice Sheet and Southern Ocean Response to Orbital Forcing from Late Miocene to Early Pliocene, Wilkes Land, East Antarctica

2021 ◽  
Author(s):  
◽  
Nikita Anne Turton
Keyword(s):  
Southern Ocean ◽  
Late Miocene ◽  
Ice Sheet ◽  
Orbital Forcing ◽  
Sea Ice Extent ◽  
Antarctic Ice Sheet ◽  
Early Pliocene ◽  
Wilkes Land ◽  
Marine Productivity ◽  
East Antarctic Ice Sheet

<p>Geological and ice sheet models indicate that marine-based sectors of the East Antarctic Ice Sheet (EAIS) were unstable during periods of moderate climatic warmth in the past. While geological records from the Middle to Late Pliocene indicate a dynamic ice sheet, records of ice sheet variability from the comparatively warmer Late Miocene to Early Pliocene are sparse, and there are few direct records of Antarctic ice sheet variability during this time period. Sediment recovered in Integrated Ocean Drilling Program U1361 drill core from the Wilkes Land margin provides a distal but continuous glacially-influenced record of the behaviour of Antarctic Ice Sheets.  This thesis presents marine sedimentological and x-ray fluorescence geochemical datasets in order to assess changes in the dynamic response of the EAIS and Southern Ocean productivity in the Wilkes Land sector during Late Miocene and Early Pliocene to climatic warming and orbital forcing between 6.2 and 4.4 Ma. Two primary lithofacies are identified which can be directly related to glacial–interglacial cycles; enhanced sedimentation during glacials is represented by low-density turbidity flows that occurred in unison with low marine productivity and reduced iceberg rafted debris. Interglacial sediments contain diatomaceous muds with short-lived, large fluxes of iceberg rafted debris preceding a more prolonged phase of enhanced marine productivity. Interglacial sediments coincide with a more mafic source of terrigenous sediment, interfered to be associated with an inland retreat of the ice margin resulting in erosion of lithologies that are currently located beneath the grounded EAIS. Poleward invigoration of the Antarctic Circumpolar Current during glacial–interglacial transitions is proposed to have intensified upwelling, enhancing nutrient availability for marine productivity, and increasing oceanic heat flux at the ice margin acting to erode marine ice sheet grounding lines and triggering retreat.  Spectral analysis of the datasets indicated orbital frequencies are present in the iceberg rafted debris mass accumulation rates at all three Milankovitch frequencies, with a dominant 100 kyr eccentricity driven ice discharge. Prolonged intervals of marine productivity correlate to 100 kyr cyclicity occurring at peaks in obliquity. The response of both ice sheet and biological systems to 100 kyr cyclicity may indicate eccentricity-modulated sea ice extent controls the influx of warm water onto the continental shelf.</p>

scholarly journals Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs

2016 ◽  
Vol 9 (3) ◽  
pp. 219-221 ◽  
Author(s):  
Luis P. A. M. Duprat ◽  
Grant R. Bigg ◽  
David J. Wilton
Keyword(s):  
Southern Ocean ◽  
Marine Productivity

scholarly journals Marine biological controls on climate via the carbon and sulphur geochemical cycles

1998 ◽  
Vol 353 (1365) ◽  
pp. 41-51 ◽  
Author(s):  
Andrew J. Watson ◽  
Peter S. Liss
Keyword(s):  
Southern Ocean ◽  
Atmospheric Circulation ◽  
Ocean Circulation ◽  
Atmospheric Carbon Dioxide ◽  
Cloud Condensation Nuclei ◽  
Climate System ◽  
Marine Biota ◽  
Marine Productivity ◽  
Clear Idea ◽  
Glacial Time

We review aspects of the influence of the marine biota on climate, focusing particularly on their role in mediating surface temperatures via their influence on atmospheric carbon dioxide (CO 2 ) and dimethyl sulphide (DMS) concentrations. Variation in natural CO 2 concentrations occurring over 10 3 to 10 5 years are set by oceanic processes, and in particular by conditions in the Southern Ocean, so it is to this region that we must look to understand the glacial–interglacial changes in CO 2 concentrations. It seems likely that marine productivity in the Southern Ocean is limited by a combination of restricted iron supply to the region and insufficient light. Plankton–produced DMS is thought to influence climate by changing the numbers of cloud condensation nuclei available in remote regions; the efficiency of this mechanism is still unknown, but calculations suggest it may be a powerful influence on climate. It has a much shorter time–scale than the CO 2 effect, and as a consequence may well be a player on the ‘global change’ timescale. The direction of both the CO 2 and the DMS mechanisms is such that more marine productivity would lead to lower global temperatures, and we speculate that the overall effect of the marine biota today is to cool the planet by ca. 6°C as a result of these two mechanisms, with one–third of this figure being due to CO 2 effects and two–thirds due to DMS. While the marine biota influence climate, climate also influences the marine biota, chiefly via changing atmospheric circulation. This in turn alters ocean circulation patterns, responsible for mixing up sub–surface nutrients, and also influences the transport of nutrients, such as iron, in atmospheric dust. A more vigorous atmospheric circulation would be expected to increase the productivity of the marine biota on both counts. Thus during glacial time, the colder and drier climate might be expected to stimulate greater marine productivity than occurs today. Since more production leads to greater cooling by reduction in CO 2 and increase in DMS, the marine biota–climate system appears to have been in positive feedback in the glacial–interglacial transition, with the changes in the climate system being reinforced by changes in the marine biota. In the context of anthropogenic change, we cannot at present say what sign the feedback on climate will have, because we have no clear idea whether circulation will become more or less vigorous in the future.

scholarly journals Variations of terrestrial input and marine productivity in the Southern Ocean (48°S) during the last two deglaciations

2000 ◽  
Vol 15 (2) ◽  
pp. 170-180 ◽  
Author(s):  
Minoru Ikehara ◽  
Kimitaka Kawamura ◽  
Naohiko Ohkouchi ◽  
Masafumi Murayama ◽  
Toshio Nakamura ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Terrestrial Input ◽  
Marine Productivity
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