Measuring air–sea gas-exchange velocities in a large-scale annular wind–wave tank
Summary: Our article presents successful gas exchange measurements obtained in a large-scale wind-wave tank. The adopted box model methodology, experimental produce and instrumentation are described in detail. For the first time, parallel measurements of total transfer velocities for 14 individual gases within a wide range of solubility have been achieved. Various wind speed conditions and the effect of surfactant layers have been investigated providing exciting results.
Comparative heat and gas exchange measurements in the Heidelberg Aeolotron, a large annular wind-wave tank
Summary: A comparative study of simultaneous heat and gas exchange measurements was performed in the large annular Heidelberg Air-Sea Interaction Facility, the Aeolotron, under homogeneous water surface conditions, including the measurement of the Schmidt number exponent. Provided the Schmidt number exponent is known and that the heated patch is large enough to reach the thermal equilibrium, it is possible to scale heat transfer velocities measured by active thermography to gas transfer velocities.
Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass – a model study
Summary: The hydrographical and ecological changes in the deep part of the Bornholm Basin in response to pumping well-oxygenated so-called winter water down to the greatest depth are investigated. By pumping 1000 m3s-1, the rates of water exchange and oxygen supply increase by 2.5 and 3 times, respectively. Anoxic bottoms should no longer occur and hypoxic events will become rare. This should mean much improved conditions for successful cod reproduction, extensive colonization of fauna on earlier periodi
An alternative method for correcting fluorescence quenching
Summary: To protect from light stress, phytoplankton inhibit photosynthesis and suppress fluorescence through the process of quenching. This makes them invisible to fluorometers. Conventionally, quenching is corrected by taking maximum fluorescence yield in a surface mixed layer (MLD) and filling in the invisible proportion. This is only valid in waters where turbulence is high and phytoplankton are uniformly mixed. Here, we show that correcting from Zeu is a robust alternative to correcting from MLD
Improved sea level record over the satellite altimetry era (1993–2010) from the Climate Change Initiative project
Summary: This paper presents various respective data improvements achieved within the European Space Agency (ESA) Climate Change Initiative (ESA CCI) project on sea level during its first phase (2010-2013), using multi-mission satellite altimetry data over the 1993-2010 time span.
M. Ablain, A. Cazenave, G. Larnicol, M. Balmaseda, P. Cipollini, Y. Faugère, M. J. Fernandes, O. Henry, J. A. Johannessen, P. Knudsen, O. Andersen, J. Legeais, B. Meyssignac, N. Picot, M. Roca, S. Rudenko, M. G. Scharffenberg, D. Stammer, G. Timms, and J. Benveniste Ocean Sci., 11, 67-82, 2015 AbstractFinal Revised Paper (PDF, 10333 KB)Discussion Paper (OSD)
13 Jan 2015
Thermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation?
Summary: The results of this study reveal that the thermohaline properties in the study area in 2011 lie between the thermohaline characteristics of the EMT and those of the pre-EMT phase, indicating a possible slow return towards the latter. It highlights the relationship between the hydrological property distribution of the upper layer in the Levantine basin and the alternate circulation regimes in the Ionian, which modulates the salinity distribution in the Eastern Mediterranean Sea.
Phytoplankton blooms on the western shelf of Tasmania: evidence of a highly productive ecosystem
Summary: This paper describes the discovery of a previously unknown coastal upwelling centre on the western coast of Tasmania, Australia. This region forms part of the Great South Australian Coastal Upwelling System, which turns out one of the largest seasonal coastal upwelling systems on Earth. Upwelling events fuel phytoplankton blooms in last austral summer months and associated coastal jets are presumably an important nutrient source for the adjacent Bass Strait.
Forecasting the mixed-layer depth in the Northeast Atlantic: an ensemble approach, with uncertainties based on data from operational ocean forecasting systems
Y. Drillet, J. M. Lellouche, B. Levier, M. Drévillon, O. Le Galloudec, G. Reffray, C. Regnier, E. Greiner, and M. Clavier Ocean Sci., 10, 1013-1029, 2014 AbstractFinal Revised Paper (PDF, 1364 KB)Discussion Paper (OSD)
12 Dec 2014
Sensitivity of phytoplankton distributions to vertical mixing along a North Atlantic transect
Summary: Measured vertical mixing profiles are applied to a 1-D phytoplankton model. Results show that shifts in vertical mixing are able to induce a transition from an upper chlorophyll maximum to a deep one and vice versa. Furthermore, a clear correlation between the surface phytoplankton concentration and mixing-induced nutrient flux is found for nutrient-limited cases. This result suggests that characteristics of the vertical mixing could be determined from the surface phytoplankton concentration.
Summary: Knowledge of the size of the Rossby radius is important, because it is the horizontal scale of boundary currents, eddies and fronts in fluids on a rotating planet. We find that, in the deep basins of the Arctic Ocean, the Rossby radius is around 10km, but in the shallow shelf seas, it can be less than 1km. This presents a challenge to measurements and models alike.
Assessment of the representation of Antarctic Bottom Water properties in the ECCO2 reanalysis
Summary: We analyzed the ability of the ECCO2 reanalysis to represent the hydrographic properties and variability of Antarctic Bottom Water in the Southern Ocean. After 2004, the opening of an oceanic polynya in the Weddell Sea sector and consequent intense dense water production leads to an unrealistic scenario. Even before 2004, bottom waters are warmer and less dense than expected, while the absolute volume transport and velocity estimates are underrepresented.
Changes in extreme regional sea surface height due to an abrupt weakening of the Atlantic meridional overturning circulation
Summary: Regional sea surface height (SSH) changes due to an abrupt weakening of the Atlantic meridional overturning circulation (AMOC) are simulated with a high- and low-resolution model. A rapid decrease of the AMOC in the high-resolution version induces shorter return times of several specific regional and coastal extremes in North Atlantic SSH than in the low-resolution version. This effect is caused by a change in main eddy pathways associated with a change in separation latitude of the Gulf Stream.
S.-E. Brunnabend, H. A. Dijkstra, M. A. Kliphuis, B. van Werkhoven, H. E. Bal, F. Seinstra, J. Maassen, and M. van Meersbergen Ocean Sci., 10, 881-891, 2014 AbstractFinal Revised Paper (PDF, 6819 KB)Discussion Paper (OSD)