TY  - JOUR
A1  - Sigman, Daniel M.
A1  - Hain, Mathis P.
A1  - Haug, Gerald H.
T1  - The polar ocean and glacial cycles in atmospheric CO2 concentration
N2  - Global climate and the atmospheric partial pressure of carbon dioxide (p(CO2atm)) are correlated over recent glacial cycles, with lower p(CO2atm) during ice ages, but the causes of the p(CO2atm) changes are unknown. The modern Southern Ocean releases deeply sequestered CO2 to the atmosphere. Growing evidence suggests that the Southern Ocean CO2 'leak' was stemmed during ice ages, increasing ocean CO2 storage. Such a change would also have made the global ocean more alkaline, driving additional ocean CO2 uptake. This explanation for lower ice-age p(CO2atm), if correct, has much to teach us about the controls on current ocean processes.
Y1  - 2010
UR  - http://www.nature.com/nature/
U6  - https://doi.org/10.1038/Nature09149
SN  - 0028-0836
ER  - 
TY  - JOUR
A1  - Brunelle, Brigitte G.
A1  - Sigman, Daniel M.
A1  - Jaccard, Samuel Laurent
A1  - Keigwin, Lloyd D.
A1  - Plessen, Birgit
A1  - Schettler, Georg
A1  - Cook, Mea S.
A1  - Haug, Gerald H.
T1  - Glacial/interglacial changes in nutrient supply and stratification in the western subarctic North Pacific since the penultimate glacial maximum
N2  - In piston cores from the open subarctic Pacific and the Okhotsk Sea, diatom-bound delta N-15 (delta N-15(db)), biogenic opal, calcium carbonate, and barium were measured from coretop to the previous glacial maximum (MIS 6). Glacial intervals are generally characterized by high delta N-15(db) (similar to 8 parts per thousand) and low productivity, whereas interglacial intervals have a lower delta N-15(db) (5.7-6.3 parts per thousand) and indicate high biogenic productivity. These data extend the regional swath of evidence for nearly complete surface nutrient utilization during glacial maxima, consistent with stronger upper water column stratification throughout the subarctic region during colder intervals. An early deglacial decline in delta N-15(db) of 2 parts per thousand at similar to 17.5 ka, previously observed in the Bering Sea, is found here in the open subarctic Pacific record and arguably also in the Okhotsk, and a case can be made that a similar decrease in delta N-15(db) occurred in both regions at the previous deglaciation as well. The early deglacial delta N-15(db) decrease, best explained by a decrease in surface nutrient utilization, appears synchronous with southern hemisphere-associated deglacial changes and with the Heinrich 1 event in the North Atlantic. This delta N-15(db) decrease may signal the initial deglacial weakening in subarctic North Pacific stratification and/or a deglacial increase in shallow subsurface nitrate concentration. If the former, it would be the North Pacific analogue to the increase in vertical exchange inferred for the Southern Ocean at the time of Heinrich Event 1. In either case, the lack of any clear change in paleoproductivity proxies during this interval would seem to require an early deglacial decrease in the iron-to-nitrate ratio of subsurface nutrient supply or the predominance of light limitation of phytoplankton growth during the deglaciation prior to Bolling-Allerod warming.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/02773791
U6  - https://doi.org/10.1016/j.quascirev.2010.03.010
SN  - 0277-3791
ER  - 
TY  - JOUR
A1  - Handy, Mark R.
A1  - Schmid, Stefan M.
A1  - Bousquet, Romain
A1  - Kissling, Eduard
A1  - Bernoulli, Daniel
T1  - Reconciling plate-tectonic reconstructions of Alpine Tethys with the geological-geophysical record of spreading and subduction in the Alps
N2  - A new reconstruction of Alpine Tethys combines plate-kinematic modelling with a wealth of geological data and seismic tomography to shed light on its evolution, from sea-floor spreading through subduction to collision in the Alps. Unlike previous models, which relate the fate of Alpine Tethys solely to relative motions of Africa, Iberia and Europe during opening of the Atlantic, our reconstruction additionally invokes independent microplates whose motions are constrained primarily by the geological record. The motions of these microplates (Adria, Iberia, Alcapia, Alkapecia, and Tiszia) relative to both Africa and Europe during Late Cretaceous to Cenozoic time involved the subduction of remnant Tethyan basins during the following three stages that are characterized by contrasting plate motions and driving forces: (1) 131-84 Ma intra-oceanic subduction of the Ligurian part of Alpine Tethys attached to Iberia coincided with Eo-alpine orogenesis in the Alcapia microplate, north of Africa. These events were triggered primarily by foundering of the older (170-131 Ma) Neotethyan subduction slab along the NE margin of the composite African-Adriatic plate; subduction was linked by a sinistral transform system to E-W opening of the Valais part of Alpine Tethys; (2) 84-35 Ma subduction of primarily the Piemont and Valais parts of Alpine Tethys which were then attached to the European plate beneath the overriding African and later Adriatic plates. NW translation of Adria with respect to Africa was accommodated primarily by slow widening of the Ionian Sea; (3) 35 Ma-Recent rollback subduction of the Ligurian part of Alpine Tethys coincided with Western Alpine orogenesis and involved the formation of the Gibraltar and Calabrian arcs. Rapid subduction and arc formation were driven primarily by the pull of the gravitationally unstable, retreating Adriatic and African slabs during slow convergence of Africa and Europe. The upper European-Iberian plate stretched to accommodate this slab retreat in a very mobile fashion, while the continental core of the Adriatic microplate acted as a rigid indenter within the Alpine collisional zone. The subducted lithosphere in this reconstruction can be correlated with slab material imaged by seismic tomography beneath the Alps and Apennines, as well as beneath parts of the Pannonian Basin, the Adriatic Sea, the Ligurian Sea, and the Western Mediterranean. The predicted amount of subducted lithosphere exceeds the estimated volume of slab material residing at depth by some 10-30%, indicating that parts of slabs may be superposed within the mantle transition zone and/or that some of this subducted lithosphere became seismically transparent.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00128252
U6  - https://doi.org/10.1016/j.earscirev.2010.06.002
SN  - 0012-8252
ER  -