Studies in the Modern Ocean

CTD/hydrocast package descending into the Southern Ocean. Photo Kenemy

The CTD/hydrocast package descending into the Southern Ocean water column from the deck of the South African research icebreaker S.A. Agulhas II, sailing from Cape Town to the Antarctic winter ice edge. Photo: Preston Cosslett Kemeny ’15

 

References

AuthorTitleTypeYear
7 Publications
Applied Filters: First Letter Of Title: O Reset
Ocean Oxygen, Preformed Nutrients, and the Cause of the Lower Carbon Dioxide Concentration in the Atmosphere of the Last Glacial Maximum
D.M. Sigman, M.P. Hain
All else equal, if the ocean s “biological [carbon] pump” strengthens, the dissolved oxygen (O2) content of the ocean interior declines. Confidence is now high that the ocean interior as a whole contained less oxygen during the ice ages. This is strong evidence that the ocean s biological pump stored more carbon in the ocean interior during the…
Oceanic nutrient rise and the late Miocene inception of Pacific oxygen-deficient zones
X.T. Wang, Y. Wang, A. Auderset, D.M. Sigman, H.A. Ren, A. Martínez-García, G.H. Haug, Z. Su, Y.G. Zhang, B. Rasmussen, A.L. Sessions, W.W. Fischer
The modern Pacific Ocean hosts the largest oxygen-deficient zones (ODZs), where oxygen concentrations are so low that nitrate is used to respire organic matter. The history of the ODZs may offer key insights into ocean deoxygenation under future global warming. In a 12-My record from the southeastern Pacific, we observe a >10 increase in…
On the Properties of the Arctic Halocline and Deep Water Masses of the Canada Basin from Nitrate Isotope Ratios
J. Granger, D.M. Sigman, J. Gagnon, J.-E. Tremblay, A. Mucci
Nitrogen is a limiting nutrient for primary production in the western Arctic Ocean. Measurements of the nitrogen (15N/14N) and oxygen (18O/16O) isotope ratios of nitrate in the southeastern Beaufort Sea provide insight into biogeochemical cycling of nitrogen in the western Arctic Ocean. Nitrate O isotope ratios in the Pacific halocline evidence a…
Onset of permanent stratification in the subarctic Pacific Ocean
G.H. Haug, D.M. Sigman, R. Tiedemann, T.F. Pedersen, M. Sarnthein

The surface waters of the modern subarctic Pacific Ocean are isolated from the nutrient-rich waters below by a steep vertical gradient in salinity (halocline), a feature which is a dominant control on upper-ocean stratification in polar environments. The physical processes which maintain the halocline and, in turn, its physical, biological, and…

The origin of NO 3 - and N 2 in deep subsurface fracture water of South Africa
B.J. Silver, R. Raymond, D.M. Sigman, M. Prokopeko, B. Sherwood Lollar, G. Lacrampe-Couloume, M.L. Fogel, L.M. Pratt, L. Lefticariu, T.C. Onstott

Deep (>0.8km depth) fracture water with residence time estimates on the order of several Ma from the Witwatersrand Basin, South Africa contains up to 40μM of NO 3 -, up to 50mM N 2 (90 times air saturation at surface) and 1 to 400μM NH 3/NH 4 +. To determine whether the oxidized N species were introduced by mining activity, by recharge of…

Origin of the deep Bering Sea nitrate deficit: Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes
M.F. Lehmann, D.M. Sigman, D.C. McCorkle, B.G. Brunelle, S. Hoffmann, M. Kienast, G. Cane, J. Clement
On the basis of the normalization to phosphate, a significant amount of nitrate is missing from the deep Bering Sea (BS). Benthic denitrification has been suggested previously to be the dominant cause for the BS nitrate deficit. We measured water column nitrate 15N/14N and 18O/16O as integrative tracers of microbial denitrification, together with…
Oxygen rise in the tropical upper ocean during the Paleocene-Eocene Thermal Maximum
S. Moretti, A. Auderset, C. Deutsch, R. Schmitz, L. Gerber, E. Thomas, V. Luciani, M.R. Petrizzo, R. Schiebel, A. Tripati, P. Sexton, R. Norris, R. D’Onofrio, J. Zachos, D.M. Sigman, G.H. Haug, A. Martínez-García
The global ocean’s oxygen inventory is declining in response to global warming, but the future of the low-oxygen tropics is uncertain. We report new evidence for tropical oxygenation during the Paleocene-Eocene Thermal Maximum (PETM), a warming event that serves as a geologic analog to anthropogenic warming. Foraminifera-bound nitrogen isotopes…