de Jong
Marieke F.
de Jong
Marieke F.
No Thumbnail Available
Search Results
Now showing
1 - 10 of 10
-
ArticleObservation-based estimates of heat and freshwater exchanges from the subtropical North Atlantic to the Arctic(Elsevier, 2021-07-06) Li, Feili ; Lozier, M. Susan ; Holliday, Naomi Penny ; Johns, William E. ; Le Bras, Isabela A. ; Moat, Bengamin I. ; Cunningham, Stuart A. ; de Jong, Marieke FemkeContinuous measurements from the OSNAP (Overturning in the Subpolar North Atlantic Program) array yield the first estimates of trans-basin heat and salinity transports in the subpolar latitudes. For the period from August 2014 to May 2018, there is a poleward heat transport of 0.50 ± 0.05 PW and a poleward salinity transport of 12.5 ± 1.0 Sv across the OSNAP section. Based on the mass and salt budget analyses, we estimate that a surface freshwater input of 0.36 ± 0.05 Sv over the broad subpolar-Arctic region is needed to balance the ocean salinity change created by the OSNAP transports. The overturning circulation is largely responsible for setting these heat and salinity transports (and the derived surface freshwater input) derived from the OSNAP array, while the gyre (isopycnal) circulation contributes to a lesser, but still significant, extent. Despite its relatively weak overturning and heat transport, the Labrador Sea is a strong contributor to salinity and freshwater changes in the subpolar region. Combined with trans-basin transport estimates at other locations, we provide new estimates for the time-mean surface heat and freshwater divergences over a wide domain of the Arctic-North Atlantic region to the north and south of the OSNAP line. Furthermore, we estimate the total heat and freshwater exchanges across the surface area of the extratropical North Atlantic between the OSNAP and the RAPID-MOCHA (RAPID Meridional Overturning Circulation and Heat-flux Array) arrays, by combining the cross-sectional transports with vertically-integrated ocean heat and salinity content. Comparisons with the air-sea heat and freshwater fluxes from atmospheric reanalysis products show an overall consistency, yet with notable differences in the magnitudes during the observation time period.
-
ArticleTwo years of observations of warm-core anticyclones in the Labrador Sea and their seasonal cycle in heat and salt stratification(American Meteorological Society, 2014-02) de Jong, Marieke F. ; Bower, Amy S. ; Furey, Heather H.Between 25 September 2007 and 28 September 2009, a heavily instrumented mooring was deployed in the Labrador Sea, offshore of the location where warm-core, anticyclonic Irminger rings are formed. The 2-year time series offers insight into the vertical and horizontal structure of newly formed Irminger rings and their heat and salt transport into the interior basin. In 2 years, 12 Irminger rings passed by the mooring. Of these, 11 had distinct properties, while 1 anticyclone likely passed the mooring twice. Eddy radii (11–35 km) were estimated using the dynamic height signal of the anticyclones (8–18 cm) together with the observed velocities. The anticyclones show a seasonal cycle in core properties when observed (1.9°C in temperature and 0.07 in salinity at middepth) that has not been described before. The temperature and salinity are highest in fall and lowest in spring. Cold, fresh caps, suggested to be an important source of freshwater, were seen in spring but were almost nonexistent in fall. The heat and freshwater contributions by the Irminger rings show a large spread (from 12 to 108 MJ m−2 and from −0.5 to −4.7 cm, respectively) for two reasons. First, the large range of radii leads to large differences in transported volume. Second, the seasonal cycle leads to changes in heat and salt content per unit volume. This implies that estimates of heat and freshwater transport by eddies should take the distribution of eddy properties into account in order to accurately assess their contribution to the restratification.
-
ArticleOverturning in the Subpolar North Atlantic Program : a new international ocean observing system(American Meteorological Society, 2017-04-24) Lozier, M. Susan ; Bacon, Sheldon ; Bower, Amy S. ; Cunningham, Stuart A. ; de Jong, Marieke Femke ; de Steur, Laura ; deYoung, Brad ; Fischer, Jürgen ; Gary, Stefan F. ; Greenan, Blair J. W. ; Heimbach, Patrick ; Holliday, Naomi Penny ; Houpert, Loïc ; Inall, Mark E. ; Johns, William E. ; Johnson, Helen L. ; Karstensen, Johannes ; Li, Feili ; Lin, Xiaopei ; Mackay, Neill ; Marshall, David P. ; Mercier, Herlé ; Myers, Paul G. ; Pickart, Robert S. ; Pillar, Helen R. ; Straneo, Fiamma ; Thierry, Virginie ; Weller, Robert A. ; Williams, Richard G. ; Wilson, Christopher G. ; Yang, Jiayan ; Zhao, Jian ; Zika, Jan D.For decades oceanographers have understood the Atlantic meridional overturning circulation (AMOC) to be primarily driven by changes in the production of deep-water formation in the subpolar and subarctic North Atlantic. Indeed, current Intergovernmental Panel on Climate Change (IPCC) projections of an AMOC slowdown in the twenty-first century based on climate models are attributed to the inhibition of deep convection in the North Atlantic. However, observational evidence for this linkage has been elusive: there has been no clear demonstration of AMOC variability in response to changes in deep-water formation. The motivation for understanding this linkage is compelling, since the overturning circulation has been shown to sequester heat and anthropogenic carbon in the deep ocean. Furthermore, AMOC variability is expected to impact this sequestration as well as have consequences for regional and global climates through its effect on the poleward transport of warm water. Motivated by the need for a mechanistic understanding of the AMOC, an international community has assembled an observing system, Overturning in the Subpolar North Atlantic Program (OSNAP), to provide a continuous record of the transbasin fluxes of heat, mass, and freshwater, and to link that record to convective activity and water mass transformation at high latitudes. OSNAP, in conjunction with the Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array (RAPID–MOCHA) at 26°N and other observational elements, will provide a comprehensive measure of the three-dimensional AMOC and an understanding of what drives its variability. The OSNAP observing system was fully deployed in the summer of 2014, and the first OSNAP data products are expected in the fall of 2017.
-
ArticleSeasonal and interannual variations of Irminger ring formation and boundary–interior heat exchange in FLAME(American Meteorological Society, 2016-05-23) de Jong, Marieke F. ; Bower, Amy S. ; Furey, Heather H.The contribution of warm-core anticyclones shed by the Irminger Current off West Greenland, known as Irminger rings, to the restratification of the upper layers of the Labrador Sea is investigated in the 1/12° Family of Linked Atlantic Models Experiment (FLAME) model. The model output, covering the 1990–2004 period, shows strong similarities to observations of the Irminger Current as well as ring observations at a mooring located offshore of the eddy formation region in 2007–09. An analysis of fluxes in the model shows that while the majority of heat exchange with the interior indeed occurs at the site of the Irminger Current instability, the contribution of the coherent Irminger rings is modest (18%). Heat is provided to the convective region mainly through noncoherent anomalies and enhanced local mixing by the rings facilitating further exchange between the boundary and interior. The time variability of the eddy kinetic energy and the boundary to interior heat flux in the model are strongly correlated to the density gradient between the dense convective region and the more buoyant boundary current. In FLAME, the density variations of the boundary current are larger than those of the convective region, thereby largely controlling changes in lateral fluxes. Synchronous long-term trends in temperature in the boundary and the interior over the 15-yr simulation suggest that the heat flux relative to the temperature of the interior is largely steady on these time scales.
-
ArticleLagrangian perspective on the origins of Denmark Strait Overflow(American Meteorological Society, 2020-08-01) Saberi, Atousa ; Haine, Thomas W. N. ; Gelderloos, Renske ; de Jong, Marieke Femke ; Furey, Heather H. ; Bower, Amy S.The Denmark Strait Overflow (DSO) is an important contributor to the lower limb of the Atlantic meridional overturning circulation (AMOC). Determining DSO formation and its pathways is not only important for local oceanography but also critical to estimating the state and variability of the AMOC. Despite prior attempts to understand the DSO sources, its upstream pathways and circulation remain uncertain due to short-term (3–5 days) variability. This makes it challenging to study the DSO from observations. Given this complexity, this study maps the upstream pathways and along-pathway changes in its water properties, using Lagrangian backtracking of the DSO sources in a realistic numerical ocean simulation. The Lagrangian pathways confirm that several branches contribute to the DSO from the north such as the East Greenland Current (EGC), the separated EGC (sEGC), and the North Icelandic Jet (NIJ). Moreover, the model results reveal additional pathways from south of Iceland, which supplied over 16% of the DSO annually and over 25% of the DSO during winter of 2008, when the NAO index was positive. The southern contribution is about 34% by the end of March. The southern pathways mark a more direct route from the near-surface subpolar North Atlantic to the North Atlantic Deep Water (NADW), and needs to be explored further, with in situ observations.
-
ArticleExtreme variability in Irminger Sea winter heat loss revealed by ocean observatories initiative mooring and the ERA5 reanalysis(American Geophysical Union, 2018-12-18) Josey, Simon A. ; de Jong, Marieke Femke ; Oltmanns, Marilena ; Moore, Kent ; Weller, Robert A.Ground‐breaking measurements from the ocean observatories initiative Irminger Sea surface mooring (60°N, 39°30′W) are presented that provide the first in situ characterization of multiwinter surface heat exchange at a high latitude North Atlantic site. They reveal strong variability (December 2014 net heat loss nearly 50% greater than December 2015) due primarily to variations in frequency of intense short timescale (1–3 days) forcing. Combining the observations with the new high resolution European Centre for Medium Range Weather Forecasts Reanalysis 5 (ERA5) atmospheric reanalysis, the main source of multiwinter variability is shown to be changes in the frequency of Greenland tip jets (present on 15 days in December 2014 and 3 days in December 2015) that can result in hourly mean heat loss exceeding 800 W/m2. Furthermore, a new picture for atmospheric mode influence on Irminger Sea heat loss is developed whereby strongly positive North Atlantic Oscillation conditions favor increased losses only when not outweighed by the East Atlantic Pattern.
-
Technical ReportImpact of Irminger Rings on Deep Convection in the Labrador Sea : mooring instrument, cruise CTD, and APEX data report September 2007 – September 2009(Woods Hole Oceanographic Institution, 2013-05) Furey, Heather H. ; McKee, Theresa K. ; de Jong, Marieke F. ; Robbins, Paul E. ; Bower, Amy S.This is the final data report of all hydrographic station, mooring, and subsurface float data collected by the Woods Hole Oceanographic Institution in 2007-2009 during the Impact of Irminger Rings on Deep Convection in the Labrador Sea experiment (IRINGS). The objectives of IRINGS were to (1) to determine the full water column hydrographic and velocity structure of newlyformed Irminger Rings that have entered the interior Labrador Sea; (2) to observe how Irminger Ring core properties are modified by atmospheric forcing over their lifetime; and (3) to improve the interpretation of sea surface height (SSH) anomalies in terms of newly formed coherent heat containing Irminger Rings. The mooring deployment and recovery cruises were both on the R/V Knorr: KN192-01 in September 2007 and KN196-01 in September 2009, respectively. The single mooring held eight Aanderaa current meters (RCM-11), two Submerged Autonomous Launch Platforms (SALPs), and nine Seabird microcats (SBE37), deployed from 26 September 2007 through 27 September 2009, yeilding full water column (100-3000 meters) records of temperature, salinity, pressure, and velocity data for the two year period. The two SALP cages contained eleven APEX floats, and released some of these floats according to local oceanographic conditions, so as to seed the floats in passing Irminger Rings, and the remainder of floats as timed releases. Thirteen conductivity-temperature-depth (CTD) stations were taken on the mooring recovery cruise, creating a boundary current cross-section from the mooring site to Nuuk, Greenland.
-
ArticleSubpolar North Atlantic western boundary density anomalies and the Meridional Overturning Circulation(Nature Research, 2021-05-24) Li, Feili ; Lozier, M. Susan ; Bacon, Sheldon ; Bower, Amy S. ; Cunningham, Stuart A. ; de Jong, Marieke F. ; deYoung, Brad ; Fraser, Neil ; Fried, Nora ; Han, Guoqi ; Holliday, Naomi Penny ; Holte, James W. ; Houpert, Loïc ; Inall, Mark E. ; Johns, William E. ; Jones, Sam ; Johnson, Clare ; Karstensen, Johannes ; Le Bras, Isabela A. ; Lherminier, Pascale ; Lin, Xiaopei ; Mercier, Herlé ; Oltmanns, Marilena ; Pacini, Astrid ; Petit, Tillys ; Pickart, Robert S. ; Rayner, Darren ; Straneo, Fiamma ; Thierry, Virginie ; Visbeck, Martin ; Yashayaev, Igor ; Zhou, ChunChanges in the Atlantic Meridional Overturning Circulation, which have the potential to drive societally-important climate impacts, have traditionally been linked to the strength of deep water formation in the subpolar North Atlantic. Yet there is neither clear observational evidence nor agreement among models about how changes in deep water formation influence overturning. Here, we use data from a trans-basin mooring array (OSNAP—Overturning in the Subpolar North Atlantic Program) to show that winter convection during 2014–2018 in the interior basin had minimal impact on density changes in the deep western boundary currents in the subpolar basins. Contrary to previous modeling studies, we find no discernable relationship between western boundary changes and subpolar overturning variability over the observational time scales. Our results require a reconsideration of the notion of deep western boundary changes representing overturning characteristics, with implications for constraining the source of overturning variability within and downstream of the subpolar region.
-
DatasetPathways to the Denmark Strait Overflow: A Lagrangian Study in the Iceland Sea(Woods Hole Oceanographic Institution, 2019-09) de Jong, Marieke Femke ; Bower, Amy S. ; Søiland, Henrik ; Furey, Heather H. ; Ramsey, Andree L.The goal of this project was to directly measure the dense water pathways upstream of the Denmark Strait in the Iceland Sea and compare the results to existing ideas about the dynamics of the circulation by deploying 45 acoustically tracked RAFOS floats over a two year time period (24-Jul-2013 to 29-May-2015). The floats were ballasted to drift at a target depth of 500m, recording pressure, temperature, and Times Of Arrivals (TOAs) every six hours or every 12 hours.
-
ArticleSeasonality of the Meridional Overturning Circulation in the subpolar North Atlantic(Nature Research, 2023-05-25) Fu, Yao ; Lozier, M Susan ; Biló, Tiago Carrilho ; Bower, Amy S. ; Cunningham, Stuart A. ; Cyr, Frédéric ; de Jong, M. Femke ; deYoung, Brad ; Drysdale, Lewis ; Fraser, Neil ; Fried, Nora ; Furey, Heather H. ; Han, Guoqi ; Handmann, Patricia ; Holliday, N. Penny ; Holte, James ; Inall, Mark E. ; Johns, William E. ; Jones, Sam ; Karstensen, Johannes ; Li, Feili ; Pacini, Astrid ; Pickart, Robert S. ; Rayner, Darren ; Straneo, Fiammetta ; Yashayaev, IgorUnderstanding the variability of the Atlantic Meridional Overturning Circulation is essential for better predictions of our changing climate. Here we present an updated time series (August 2014 to June 2020) from the Overturning in the Subpolar North Atlantic Program. The 6-year time series allows us to observe the seasonality of the subpolar overturning and meridional heat and freshwater transports. The overturning peaks in late spring and reaches a minimum in early winter, with a peak-to-trough range of 9.0 Sv. The overturning seasonal timing can be explained by winter transformation and the export of dense water, modulated by a seasonally varying Ekman transport. Furthermore, over 55% of the total meridional freshwater transport variability can be explained by its seasonality, largely owing to overturning dynamics. Our results provide the first observational analysis of seasonality in the subpolar North Atlantic overturning and highlight its important contribution to the total overturning variability observed to date.