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The North Atlantic Ocean and Climate Observing SystemStuart A. CunninghamScottish Association for Marine ScienceStuart.Cunningham@sams.ac.uk Barbara Berx1, Eleanor Frajka-Williams2 and Mark Inall3

1Marine Laboratory Science, Aberdeen,2National Oceanography Centre, University of Southampton, 3SAMS.

MASTS ASM, Herriot Watt, August 2013Who am I, Thanks to co-authors.Past decade, large-scale, sustained observations of ocean circulation. By large-scale I mean basin scale observations that attempt to measure all components of the circulation.Cant cover all aspects of the Observing System, so in the end this is a rather personal view, but I am trying to emphasise aspects of the infrastructure of the observing system that is ripe for exploitation for interdisciplinary long term studies.1Tickling the Dragons TailThe Role of the Atlantic in Global Climate

Climate is the o-a combined heat flux away from the equator.High latitude deep water formation, Eh north, 25% of the global ocean-atmosphere heat flux.MOC carries the heat flux.1.3PW ocean heat flux -> atmosphere between 26 & 50N -> UK/western Europe 5-10C warmer than other regions at similar latitude (e.g. Siberia).Climate impacts e.g. SST and hurricanes in the subtropics; SST and the ITCZ and rainfall patterns in Amazon Basin and Sahel. Sea level e.g. US east coastEfficiency of CO2 sequestration into deep ocean is related to the rates of deep water formation.The Atlantic is important for the transport and storage of excess CO2: inventories of excess CO2 show that the North Atlantic stores 23% of the total global ocean inventory (the Southern Ocean, relative to the Atlantic has low concentrations of excess CO2 but contains about 60% of the total because of its larger area). Northward of 24.5N in the Atlantic, excess CO2 is accumulating at a rate of 0.43GtC/yr. The meridional overturning circulation (MOC) carries 0.24GtC/yr northward and 0.19GtC/yr is taken up through the atmosphere ([Alvarez, et al., 2003]). The global cycle of excess CO2 begins with emissions to the atmosphere in the northern hemisphere, some absorption by the ocean and by the northern hemisphere land based ecosystems, while the remainder is transported to the southern hemisphere by the atmosphere where there is a net atmosphere to ocean flux. The ocean then transports part of this back to the northern hemisphere principally the North Atlantic where it accumulates.On timescales of decades or longer there is a positive feedback between increasing ocean CO2 concentrations and a decrease in absorption of excess CO2 by the ocean ([Sabine, et al., 2004]). As the oceans acidify their efficiency in absorbing excess CO2 from the atmosphere diminishes. [Sabine, et al., 2004] show that from 1800 to 1994 the oceans absorbed 48% of the excess CO2, but in the period 1980 to 1999 this reduced to 31%.The pre-industrial ocean flux of carbon is southward across the equator and in the north Atlantic is about six times larger and of opposite sign to the excess flux at 24.5N. Typically there is out gassing of carbon in the tropics and uptake in the subpolar regions of deep water and intermediate water formation. Because the atmospheric and oceanic flux of excess CO2 is opposed to the pre-industrial carbon flux the present day carbon cycle is relatively weaker.Slowing of the MOC (IPCC)

The Sustained Observations are: Satellites, Argo (T/S to 2000m not boundaries, deep argo being developed), Inflow & Overflow Arrays, MOC arrays, Ship surveys (critical for defining the long-term evolution of ocean properties particularly the biogeochemistry). Important distinction between argo (largely an inventory tool) and flux arrays (dynamics of the system).2The strategic focus for MASTS Deep Sea ResearchSustained observations of the varying and evolving ocean circulation.Analysis and interpretations of observations for comparison with climate models.Focused field experiments to understand ocean processes not resolved in coupled climate models so these processes may be better represented in models.

This will rely on:New Technologies (platforms, sensors, power).Enhancement of sustained observation programmes (in time, space and parameters).Multi-disciplinary teams of brilliant scientists focused on strategic research issues.Definition of ocean circulation: Physical, chemical and biological properties (currents, temperature, salinity, sea-surface level, oxygen, nitrate, carbon dioxide, phytoplankton etc.)Sustained Observations of the Varying and Evolving OceanStrategic focus of MASTS deep-seas research must be to observe the patterns of climate change in the ocean, to interpret the observations to understand the process of climate change and to improve our ability to accurately predict the course of climate change globally and regionally.Long time series establish the amplitude and variability on sub-annual, seasonal and inter-annual timescales against which climate change on decadal timescales can be assessed.Monitoring establishes the spatial pattern of decadal changes which are essential for assessing the mechanisms of change.Comparing spatial pattern of change of model predictions with and without anthropogenic forcing establishes whether the decadal changes are the result of natural variability or anthropogenically driven change.Ocean State Estimation

Estimating the Circulation and Climate of the Ocean (ECCO)Aim: to produce increasingly accurate syntheses of all available global-scale ocean and sea-ice data at resolutions that start to resolve ocean eddies and other narrow current systems, which transport heat, carbon, and other properties within the ocean.

MIT OGCM0.3-1 resolution1993-now

Monthly, 10-day, daily or 12-hourly ocean model state, adjusted forcing fields and mixing coefficients.

Atlantic-Nordic/Arctic Ocean Inflows & Outflows

Atlantic Inflows to the Nordic Seas (e.g. FSC, Marlab)Atlantic Outflows (FBC, Iceland Ridge, Denmark Strait, Davis Strait)

FSC annual since 1903 (T S Chlorophyll, Nuts)6

Lab Sea Exit ArrayLine W @ 35NRAPID @ 26.5NMOVE @ 16NSAMOC @ 35S

From 1996

Since 2004

Deep Western Boundary Current Flux ArraysFSC annual since 1903 (T S Chlorophyll, Nuts)7Sustained Observations of the Atlantic Meridional Overturning Circulation at 26.5N2004-2021

The RAPID array at 26.5NCunningham, S. A. et al. (2007). "Temporal variability of the Atlantic Meridional Overturning Circulation at 26.5N." Science 317(17 Aug 2007): 935-938.8

Sustained Observations of the Varying and Evolving OceanSurface to ~1100m1100m to 5000mExplain plotThis is why I am emphasising long time series: to quantify the amplitude of variability on sub-annual, seasonal and interannual timescales against which change on decadal timescales can be assessed: A question of statiistics.BUT it is also about analysis and interpretation.9Sub-Tropical Atlantic Ocean Heat Content

Cunningham, S. A., et al., (2013). "Atlantic Meridional Overturning Circulation slowdown causes widespread cooling in the Atlantic." Geophys. Res. Letters submitted.Slowing of the AMOC

1.6 to 2.7 Sv slowdownSmeed, McCarthy and Cunningham 2013: Slowing of the AMOC, Ocean Sci. Discussion, submitted.Slowing of the AMOC

1.6 to 2.7 Sv slowdownSlowing of the AMOC

1.6 to 2.7 Sv slowdownDuring the time of the 26N array observations there has been a predominantly negative NAO10 (Figure 7). Associated with the negative NAO is a tripole SST pattern with cooler mid11latitudes and warm subtropics. Cunningham et al., (2013) suggested that the AMOC has a12 role in setting sub-surface temperature anomalies, which have been linked to re-emerging13 SST patterns and subsequent anomalies in the NAO (Taws et al., 2011). The results14 presented here are consistent with AMOC driven changes to the SST tripole pattern but they15 are not sufficient to conclude a causal relationship. Li et al., (2012) found an anti-correlation16 between sea-surface height (SSH) between 30 and 50 N in the Atlantic and accumulated17 (i.e. time integrated) NAO. If SSH changes primarily reflect variations in heat content this18 also supports the association of reducing AMOC and negative NAO.19 In Figure 7 we show the data from the 26N observations superimposed on the accumulated20 NAO and the index for the Atlantic Multidecadal Oscillation (AMO). To date the length of21 the 26N time series is short compared with timescale of the low frequency variability of the22 AMO (of the order of 60 years). However, snapshots of the AMOC were made in23 hydrographic cruises going back to 1957 and these are also shown on Figure 7. The values24 are taken from Table 5 in (Atkinson et al., 2012), which compared all six section from 1957,25 1981, 1992, 1998, 2004 and 2010 and adjusted the figures to remove the effect of the seasonal26 variability as determined from the 26N observations. However, we used annual average27 values for the Ekman and Gulf Stream components. The error bars on the hydrographic28 estimates are though too large draw any conclusions about the association of the AMOC with29 the NAO or AMO. Bryden et al. (2005) suggested that the errors could be as large as 6 Sv.30 In fact the AMOC measured by the hydrographic cruise in 2010 was stronger than that in31 2004. This underlines the fact that continuous observations are required to determine the32 variability of the AMOC.13

About GO-SHIPDespite numerous technological advances over the last several decades, ship-based hydrography remains the only method for obtaining high-quality, high spatial and vertical resolution measurements of a suite of physical, chemical, and biological parameters over the full water column. Ship-based hydrography is essential for documenting ocean changes throughout the water column, especially for the deep ocean below 2 km (52% of global ocean volume not sampled by profiling floats). Global hydrographic surveys have been carried out approximately every decade since the 1970s through research programs such as GEOSECS, TTO/SAVE, WOCE / JGOFS, and CLIVAR. However, global repeat hydrography has lacked formal global organization since the end of WOCE and this has led to a lack of visibility for hydrography in the global observing system as well as a significant decrease in the number of trans-basin sections carried out by some countries. More importantly, the lack of international agreements for implementation of hydrographic sections has led to disparate data sharing policies, duplication of some sections, and sections being carried out without the full suite of core variables.

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Ocean Observatories Initiative2014 to 2039http://oceanobservatories.org

Irminger Sea NodeAir-sea fluxes of heat, moisture and momentum.Physical, biological and chemical properties throughout the water column.Geophysical observations made on the sea-floor.Horizontally fixed platforms (moorings).Moored profilers to sample the full water column.Mobile platforms (gliders) for spatial and temporal sampling capabilities.NSF Funded 25-year programme.Transforming Ocean ResearchThe OOI will transform research of the oceans by establishing a network of interactive, globally distributed sensors with near real-time data access, thereby enhancing our capabilities to address critical issues such as climate change, ecosystem variability, ocean acidification, and carbon cycling.Recent technological advances in sensors, computational speed, communication bandwidth, Internet resources, miniaturization, genomic analyses, high-definition imaging, robotics, and data assimilation, modeling, and visualization techniques are opening new possibilities for remote scientific inquiry and discovery.The OOI will enable innovative developments across all of these fields and will contribute to maintaining American leadership in scientific advancement as well as providing exceptional educational opportunities.Final Network Design (updated April 2010)Project Execution Plan (Nov 2009)Through One Integrated Observing SystemThe OOI will enable multiple scales of marine observations that are integrated into one observing system via common design elements and an overarching, interactivecyberinfrastructure. Thecoastal-scale assetsof the OOI will expand existing observations off both U.S. coasts, creating focused, configurable observing regions.Regional cabled observing platformswill wire a single region in the Northeast Pacific Ocean with a high speed optical and high power grid. The global component addresses planetary-scale changes via moored open-ocean buoys linked to shore via satellite.

Irminger Sea NodeThe global component of the OOI design includes a network of moorings at critical, yet under-sampled, high-latitude locations such as within the Irminger Sea, southeast of Greenland. Moorings located in the Irminger Sea will support sensors for measurement of air-sea fluxes of heat, moisture and momentum; physical, biological and chemical properties throughout the water column; and geophysical observations made on the sea-floor. The array will have a combination of horizontally fixed platforms (moorings) with moored profilers to address the requirement to sample the full water column and mobile platforms (gliders) that will provide simultaneous spatial and temporal sampling capabilities. The array will be composed of a Surface Mooring containing fixed instruments situated on the buoy and through the top 1500 m of the water column. A subsurface Global Hybrid Profiler Mooring will be situated close to the surface mooring and will be made up of two types of profilers: a surface piercing profiler operating from ~150 m to the surface, allowing for satellite data telemetry, and a wire following profiler operating from ~240 m to 2400 m. Two additional subsurface Mesoscale Flanking moorings will be deployed to form a triangular array ~20 km on a side. These flanking Moorings have their uppermost flotation at ~40 m depth and instruments at discrete depths along the mooring line. Gliders will be equipped with acoustic modems to relay data to shore via satellite telemetry and will sample within and around the triangular array. These gliders will carry sensor suites (see below) with the capability to alter sampling rates during a mission.

3.1 Fundamental Data PolicyIn principle, all OOI data will be made publicly available, free of charge, to anyone. Data will be madeavailable as quickly as feasible (i.e., there will be no delays in distribution for non-technical, non-securityreasons). The User is granted the right to use OOI data and web sites for any legal and non-prohibitedpurpose whatsoever (further discussed in the User Terms and Conditions) -- to access, link to and use,create derivative works, publish, distribute, disseminate, transfer, or copy. Two possible exceptions to thispolicy are when the data impact national15Observing the Sub-Polar North Atlantic Programme2013-2018

The OSNAP line, comprising: (A) German 53N western boundaryarray and Canadian shelf-break array; (B) US West Greenland boundary array;(C) US/UK East Greenland boundary array; (D) Netherlands western Mid-Atlantic Ridge array; (E) US eastern Mid-Atlantic Ridge array; (F) UK glidersurvey (yellow) over the Rockall-Hatton Plateau and Rockall Trough; (G) UKRockall Trough and Scottish Slope Current array. Red dots: US float launchsites. Blue star: US OOI Irminger Sea global node. Black concentric circles:US sound sources.The Atlantic MOC and the subpolar gyreMotivation for focus on the subpolar gyre

16Fluxes Across Sloping Topography of the North East Atlantic

The use of multiple AUVs in FASTNEt: a study of Ocean Shelf ExchangeMark Inall

Internal tide generation at the shelf break

And decay and mixing on shelf

Exchange drainage in the bottom boundary

Internal tide generation at the shelf break

And decay and mixing on shelf

Exchange drainage in the bottom boundary

Internal tide generation at the shelf break

And decay and mixing on shelf

Exchange drainage in the bottom boundary

Standard Glider Pairs+ Turbulence Glider+ AutoSub Long Range (planned)

Internal tide generation at the shelf break

And decay and mixing on shelf

Exchange drainage in the bottom boundary

SummaryDeep Seas needs to have a motivating strategic focus

Sustained ObservationsAnalysis and interpretation (for understanding and to compare to climate models)Focused field experiments/process studies

Opportunities:New Technologies (platforms and sensors)Enhancement of existing arrays (RAPID, OSNAP, OOI, Argo)Multi-disciplinary teams of brilliant scientistsThe research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299NACLIM www.naclim.eu