In early November scientists from both sides of the Atlantic travelled to the National Oceanography Centre in Southampton, UK to spend two days discussing new
The OSNAP and OOI scientists at the 2017 Irminger Sea Regional Science Workshop, 8-9 November 2017, hosted by the National Oceanography Centre, UK.
findings and future research. The 2017 Irminger Sea Regional Science Workshop was designed to give us time to present results from recent observations from OSNAP and the Ocean Observatories Initiative (OOI http://oceanobservatories.org/), and to develop plans for collaborative analyses, publications and sampling strategies.
Workshops are less formal than conferences, and because this workshop was limited to less than 40 people there was much opportunity for conversation between all the participants. We had a good mixture of established and early career scientists, and for me that meant a chance to meet some new people, and to get to know better some people I’d met only briefly at previous OSNAP meetings.
We spent the first day sharing short talks on our analyses – and often these were presentations of preliminary results, giving the meeting an air of excitement. Each talk prompted lots of questions as we related our own findings to those up on the screen in front of us. The discussions spilled over into breaks and many people commented to me about how useful those conversations have been to them – this is the reason why we hold these workshops.
Some highlights among the talks were from OSNAP scientists – there isn’t room to list them all here, but here are a selection. Bob Pickart opened the talk session by showing us early results from his array west of Greenland – describing rapidly passing deep cyclones that may originate east of Greenland, and telling a great story about an instrument being torn off a mooring by ice, which was transported by the iceberg for a while before being found and returned by fishermen. Femke de Jong showed very interesting differences in variability at 3 closely-located mooring sites, concluding that controls on variability can change over small spatial scales. Johannes Karstensen presented some fascinating maps of mid-depth circulation derived from Argo float displacements, highlighting narrow and fast routes for exchange between the Labrador and Irminger Seas. Amy Bower, giving her talk remotely from the US, showed us more lagrangian information – this time intriguing tracks from floats that stay within the dense overflow layers and create a pattern of pathways quite different to our schematic maps. Isabela LeBras is exploring the slightly different seasonal cycles revealed by OSNAP moorings in the East Greenland Coastal Current and it’s larger offshore neighbour the East Greenland Current, and Peigen Lin showed us how the the inner current evolves as it travels around Cape Farewell. We finished the talks with a session on biogeochemical measurements on moorings, floats and gliders, and how changes in physical processes can impact ecosystems, reviving for some of us the idea that it would be very beneficial to build a biogeochemical programme associated with OSNAP.
The second day was even more interactive. We started by brain-storming ideas for research, writing down any science questions that came to mind: big, small, obvious questions, crazy ideas. We grouped them into themes and those became the topics for small breakout groups for the rest of the day. This brought people with common interests together and encouraged everyone to share their thoughts and ideas. Our discussion groups were: biogeochemical and physical interaction, boundary processes and exchange with the interior, air-sea interaction, convection and re-stratification, ice and freshwater, and large-scale connectivity. We came away from this day’s work with new ideas, plans for new collaborative papers, and some new networks of scientists interested in specific topics.
The conversations we started at this workshop will continue online and at future science meetings, and hopefully another workshop in a few years time.
Monday, 24 Apr 2017
The North Atlantic: natural variability and global change (co-organized)
OS1.2/AS1.20/CL1.29
Oral Presentations: Location: Room D2
On the Nature of the Mesoscale Variability in Denmark Strait
Robert Pickart, Wilken von Appen, Dana Mastropole, Hedinn Valdimarsson, Kjetil Vage, Steingriumur Jonsson, Kerstin Jochumsen, and James Girton
EGU2017-5372
09:00-09:15 View Abstract
OSNAP Update: Measuring the AMOC in the subpolar North Atlantic
M Susan Lozier
EGU2017-10341
10:30–10:45 View Abstract
Overflow Water Pathways in the Subpolar North Atlantic Observed with Deep Floats
Amy Bower, Heather Furey, and Susan Lozier
EGU2017-8103
11:00–11:15 View Abstract
Observed and Modeled Pathways of the Iceland Scotland Overflow Water in the eastern North Atlantic
Sijia Zou, Susan Lozier, Walter Zenk, Amy Bower, and William Johns
EGU2017-9794
11:15-11:30 View Abstract
Transport of Iceland-Scotland Overflow waters in the Deep Western Boundary Current along the Reykjanes Ridge
William Johns, Adam Houk, Greg Koman, Sijia Zou, and Susan Lozier
EGU2017-9415
11:30–11:45 View Abstract
Gulf Stream transport and mixing processes via coherent structure dynamics
Chris Wilson, Yi Liu, Melissa Green, and Chris Hughes
EGU2017-10345
14:00–14:15 View Abstract
Transport Structure and Energetic of http://buylexaprousa.com the North Atlantic Current in Subpolar Gyre from Observations
Loïc Houpert, Mark Inall, Estelle Dumont, Stefan Gary, Marie Porter, William Johns, and Stuart Cunningham
EGU2017-5593
14:30–14:45 View Abstract
Poster Presentations
Location: Hall X4
Time: 17:30–19:00
Volume, heat and freshwater transport in the Irminger Current
M. Femke de Jong, Laura de Steur, Stelios Kritsotalakis
EGU2017-9635
X4.28 View Abstract
Assessing variability in the size and strength of the North Atlantic subpolar gyre
Nick Foukal and Susan Lozier
EGU2017-10141
X4.6 View Abstract
Transport and seasonal variability of the East Reykjanes Ridge Current
Greg Koman, Adam Houk, Cobi Christiansen, and Bill Johns
EGU2017-8490
X4.43 View Abstract
On the Linkage between Labrador Sea Water Volume and Overturning Circulation in the Labrador Sea
Feili Li and Susan Lozier
EGU2017-9776
X4.48 View Abstract
Application of a Regional Thermohaline Inverse Method to observational reanalyses in an Arctic domain
Neill Mackay, Chris Wilson, and Jan Zika
EGU2017-17329
Poster: X4.60 View Abstract
The AMOC as a mechanism for nutrient supply to the Eastern North Atlantic
Ryan Peabody and Susan Lozier
EGU2017-17315
X4.56 View Abstract
Gyre scale deep convection in the subpolar North Atlantic Ocean during winter 2014-2015
Anne Piron, Virginie Thierry, Herlé Mercier, and Guy Caniaux
EGU2017-10183
X4.49 View Abstract
Circulation in the region of the Reykjanes Ridge in June-July 2015
Petit Tillys, Mercier Herle, and Thierry Virginie
EGU2017-13328
X4.25 View Abstract
Tuesday, 25 Apr 2017 Room: G2
Mesoscale eddies control meridional heat flux variability in the subpolar North Atlantic
Jian Zhao, Amy Bower, Jiayan Yang, Xiaopei Lin, and Chun Zhou
EGU2017-17050
09:15-09:30 View Abstract
Neill Mackay
03:15-03:30 PM
Room 228-230
PO13E-06: Circulation and mixing in the subpolar North Atlantic diagnosed from climatology using a Regional Thermohaline Inverse Method (RTHIM)
The Overturning in the Subpolar North Atlantic Program (OSNAP) aims to quantify the subpolar Atlantic Meridional Overturning Circulation (AMOC), including associated advective and diffusive transport of heat and freshwater. The OSNAP observational array will provide a continuous subpolar record of the AMOC from Labrador-Greenland-Scotland during 2014-2018. To understand the significance of high- and low- frequency changes measured by the array, including changes to AMOC metrics, water mass transformation and transports, Argo observations provide a useful complementary constraint for an inverse method, with the aim of resolving intra-seasonal timescales.
A novel inverse method in thermohaline coordinates has recently been demonstrated as being able to diagnose aspects of the global overturning circulation and mixing from model data. Here we have further developed a Regional Thermohaline Inverse Method, (RTHIM) and have validated it with the NEMO model in the OSNAP region, before applying it to a seasonal Argo climatology.
In an ocean basin there exists a balance between surface heat and freshwater fluxes, advective fluxes at an open boundary and interior diffusive mixing. RTHIM makes use of this balance to determine unknown velocities at the open boundary and diffusive fluxes of heat and salt within http://www.buypropeciaonline.org the domain volume. We identify key transport and mixing regions and events, relevant to the subpolar AMOC, and discuss the robustness of the inverse solutions. RTHIM is also able to identify the particular contributions to AMOC volume transport changes from temperature and salinity components.
Tuesday, 23 February
Susan Lozier
Plenary lecture
10:30–11:30 AM
Great Hall A&B
A Decade after The Day After Tomorrow: Our Current Understanding of the Ocean’s Overturning Circulation
In 1800 Count Rumford ascertained the ocean’s meridional overturning circulation from a single profile of ocean temperature constructed with the use of a rope, a wooden bucket and a rudimentary thermometer. Over two centuries later, data from floats, gliders and moorings deployed across the North Atlantic has transformed our understanding of the temporal and spatial variability of the meridional overturning: the component of the climate system responsible for sequestering heat and anthropogenic carbon dioxide in the deep ocean. In this talk I will review our current understanding of the overturning circulation with a particular focus on what we currently do and don’t understand about the mechanisms controlling its temporal change.
Thursday, February 25, 2016
Ric Williams
08:00-08:15 AM
Rooms 211-213
PC41A-01 Climate sensitivity to ocean sequestration of heat and carbon.
Ocean ventilation is a crucial process leading to heat and anthropogenic carbon being sequestered from the atmosphere. The rate by which the global ocean sequesters heat and carbon has a profound effect on the transient global warming. This climate response is empirically defined in terms of a climate index, the transient climate response to emissions (TCRE). Here, we provide a theoretical framework to understand how the TCRE can be interpreted in terms of a product of three differential terms: the dependence of surface warming on radiative forcing, the fractional radiative forcing contribution from atmospheric CO2 and the dependence of radiative forcing from atmospheric CO2 on cumulative carbon emissions. This framework is used to diagnose two models, an Earth System Model of Intermediate Complexity, configured as an idealised coupled atmosphere and ocean, and an IPCC-class Earth System Model. In both models, the centennial trends in the TCRE are controlled by the response of the ocean, which acts to sequester both heat and carbon; there is a decrease in the dependence of radiative forcing from CO2 on carbon emissions, which is partly compensated by an increase in the dependence of surface warming on radiative forcing. On decadal timescales, there are larger changes in the TCRE due to changes in ocean heat uptake and changes in non-CO2 radiative forcing linked to other greenhouse gases and aerosols. Our framework may be used to interpret the response of different climate models and used to provide traceability between simple and complex climate models.
Helen Johnson
08:45 – 09:00am
Rooms 203-205
PO41A-04 Dynamical Attribution of Recent Variability in Atlantic Overturning
Attributing observed variability of the Atlantic Meridional Overturning Circulation (AMOC) to past changes in surface forcing is challenging but essential for detecting any influence of anthropogenic forcing and reducing uncertainty in future climate predictions. Here we obtain quantitative estimates of wind and buoyancy-driven AMOC variations at 25?N by projecting observed atmospheric anomalies onto model-based dynamical patterns of AMOC sensitivity to surface wind, thermal and freshwater forcing over the preceding 15 years. We show that local wind forcing dominates AMOC variability on short timescales, whereas subpolar heat fluxes dominate on decadal timescales. The reconstructed transport time series successfully reproduces most of the interannual variability observed by the RAPID-MOCHA array. However, the apparent decadal trend in the RAPID-MOCHA time series is not captured, requiring improved model representation of ocean adjustment to subpolar heat fluxes over at least the past two decades, and highlighting the importance of sustained monitoring of the high latitude North Atlantic.
Patricia Handmann et al
09:30 – 09:45 AM
Rooms 203-205
PO41A-07 North Atlantic Deep Western Boundary Current Dynamics as Simulated by the VIKING20 Model Compared with Labrador Sea Observations
The connection of dynamic and hydrographic properties simulated by the VIKING20 model driven by CORE2 atmospheric forcing will be presented and compared to more than decade-long observations at the exit of the Labrador Sea near 53°N. VIKING20 is a high resolution (1/20°) nest, implemented by two-way nesting in a global configuration of the NEMO-LIM2 ocean-sea ice model in the North Atlantic (ORCA25). The exit of the Labrador Sea is the place where water masses from different origins and pathways meet and which are collectively called North Atlantic Deep Water (NADW). The VIKING20 flow field on average reproduces the observed structure as well as the bottom intensification of the western boundary current at 53°N. Here, we investigate the properties of the observed and modeled deep western boundary current by comparing North Atlantic water masses and currents simulated by the high resolution model with moored and hydrographic data from almost 20 year-long observations at 53°N. As comparable density fields in the model in comparison to the observations are found at shallower depths, we will present an evaluation of dynamic and hydrographic changes connected to each other and to atmospheric forcing in the model and observed data. In addition the following key questions will be addressed: How is energy distributed in baroclinic and barotropic components in observations and model in comparison to each other? The seasonal cycle can be found in the shallow Labrador Current in the model and the observations, but how deep is it reaching and causing dynamic and hydrographic changes?
Stuart Cunningham et al
03:00 – 03:15 PM
Rooms 203-205
O43A-05: The Subpolar AMOC: Dynamic Response of the Horizontal and Overturning Circulations due to Ocean Heat Content Changes between 1990 and 2014
Ocean heat content (OHC) in the subpolar region of the North Atlantic varies on interannual to decadal timescales and with spatial variations between its sub-basins as large as the temporal variability. In 2014 the Overturning in the Subpolar North Atlantic Programme (OSNAP) installed a mooring array across the Labrador Sea and from Greenland to Scotland. The objective of the array is to measure volume, heat and fresh-water fluxes. By combining Argo and altimeter data for the period 1990 to 2014 we describe and quantify the anomalous horizontal and overturning circulations and fluxes of heat and fresh-water driven by the long-term OHC changes. We thus provide a longer-term context for the new observations being made as part of OSNAP. Changes to the horizontal circulation involve deceleration of the gyre rim currents, lateral shifts of major open ocean current features and increased exchanges in the eastern intergyre region. These changes impact the Atlantic Meridional Overturning Circulation (AMOC) in density space causing a rich vertical anomalous structure. The net impact over this 24 year period is a reduction in northward heat-flux and decrease in southward fresh-water flux.
Friday, February 26, 2016
Johannes Karstensen et al
03:00 – 03:15 PM
Rooms 203-205
PO53A-05: Observations and causes of hydrographic variability in den deep western boundary current at the exit of the Labrador Sea.
The hydrographic variability of the Deep Western Boundary Current (DWBC) in the Labrador Sea is discussed using observational data from the period 1997 to 2014. This variability of the DWBC occurs on time scales from a few days to multiannual. The hydrographic data is analyzed in terms of signals originating from different “behavioral modes” of the DWBC, including the re-positioning of the core along the sloping topography, the pulsing of the core, and the advection of watermass anomalies within the core. Cross-correlation spectra show that the hydrographic variability on time scales of a few days can be explained by the periodic re-location of the core due to topographic waves. Variability on longer time scales can be interpreted by long-term re-location of the core, potentially related to an adjustment of the core to circulation changes on gyre scale. However, along-flow advection of anomalies is likely another source for this long-term variability. Possible scenarios for the generation of hydrographic variability in the source regions of the DWBC are discussed.
Poster Presentations
Monday, February 22, 2016 04:00 PM – 06:00 PM
Ernest N. Morial Convention Center, Poster Hall
HE14B High Latitude Air-Sea-Ice Interactions in a Changing Climate II Posters
Marilena Oltmanns et al
HE14B-1415: The Role of Local and Regional Atmospheric Forcing for Convection in the Subpolar North Atlantic
https://agu.confex.com/agu/os16/meetingapp.cgi/Paper/92491
Tuesday, February 22, 2016 04:00 PM – 06:00 PM
Ernest N. Morial Convention Center, Poster Hall
PO24B: Mesoscale and Submesoscale Processes: Characterization, Dynamics, and Representation VI Posters
Chris Wilson
PO24B-2949: An Update to the ‘Barrier or Blender’ Model of the Gulf Stream, Based on Lagrangian Analysis of Aviso Altimetry.
Thursday, February 25, 2016 04:00 PM – 06:00 PM
Ernest N. Morial Convention Center, Poster Hall
PO44 Atlantic Meridional Overturning Circulation: Past, Present, and Future III Posters
Chun Zhou PO44A-3118: Subpolar North Atlantic glider observations for OSNAP
Friday, February 26, 2016 04:00 PM – 06:00 PM
Ernest N. Morial Convention Center, Poster Hall
PO54A: Atlantic Meridional Overturning Circulation: Past, Present, and Future V Posters
Amy Bower PO54A-3225: The Charlie-Gibbs Fracture Zone: A Crossroads of the Atlantic Meridional Overturning Circulation
Nicholas Foukal and Susan Lozier PO54A-3229: Variability in Lagrangian-derived througput from the subtropical to the subpolar gyres in the North Atlantic and its impact on inter-gyre heat transport.
Penny Holliday PO54A-3222: The AMOC and subpolar gyre circulation at the OSNAP section in summer 2014.
Ric Williams PO44A-3130: Gyre-specific Ocean Heat Content Changes Controlled by the Meridional Overturning in the North Atlantic
Sijia Zou PO54A-3224: Contradictory Pathways between Labrador Sea Water Advection and Property Propagation.
PO54B: Climate Trends, Hydrographic Variability, Circulation, and Air-Land-Sea Interactions in the Marginal Seas of the North Atlantic III Posters
Femke de Jong & Laura de Steur PO54B-3241: Record deep convection in the Irminger Sea: Observations from the LOCO mooring during winter 2014-2015.
Laura de Steur & Femke de Jong PO54B-3242: Transport variability of the Irminger Current: First year-round results from a mooring array on the Reykjanes Ridge.
Loïc Houpert PO54B-3234: Glider Observations of the Properties, Circulation and Formation of Water Masses on the Rockall Plateau in the North Atlantic.
Virginie Thierry PO54B-3239: Argo float observations of basin-scale deep convection in the Irminger Sea during winter 2011-2012.
OSNAP will be well represented at the 2014 AGU Fall Meeting! Many of the scientist who have written for the blog will be giving presentations on their work. This will be a great opportunity to get a more in depth look at ongoing OSNAP research. A list of talks and poster presentations relating to OSNAP are below.
OS41G The Atlantic Meridional Overturning Circulation, Climate Variability, and Change I Thursday, December 18, 2014 08:00 AM – 10:00 AM Moscone West 3009
Amy S Bower, Heather H Furey and Xiaobiao Xu
New Direct Estimates of Iceland-Scotland Overflow Water Transport Through the Charlie-Gibbs Fracture Zone, OS41G-02
08:15 AM
David Philip Marshall, Helen R Pillar, Patrick Heimbach and Helen Louise Johnson
Attributing Variability in Atlantic Meridional Overturning to Wind and Buoyancy buy cipro online Forcing, OS41G-03 (Invited)
08:30 AM
Ric Williams
Impact of Gyre-Specific Overturning Changes on North Atlantic Heat Content
08:45 AM
Martin Visbeck, Jürgen Fischer, Johannes Karstensen and Rainer Zantopp
Decadal Variations of the Atlantic Meridional Overturning Circulation
09:45 AM
OS42BThe Atlantic Meridional Overturning Circulation, Climate Variability, and Change II Thursday, December 18, 2014 10:20 AM – 12:20 PM Moscone West 3009
Igor Yashayaev, John Loder and Miguel Angel Morales Maqueda
Recurrence of Winter Convection in the Warming Labrador Sea and Associated Variability Downstream
11:20 AM
OS43D The Atlantic Meridional Overturning Circulation, Climate Variability, and Change III Posters Thursday, December 18, 2014 01:40 PM – 06:00 PM Moscone West, Poster Hall
Nicholas Foukal and Susan Lozier
Lagrangian Pathways of Temperature Anomalies from the Subtropical to the Subpolar Gyre in the North Atlantic (OS43D-1300)
