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  • 1
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    Multidecadal variability of potential temperature, salinity, and transport in the eastern subpolar North Atlantic (2015)
    Wiley
    Details
    Publication Date: 2015-08-14
    Description: The Extended Ellett Line (EEL) hydrographic section extends from Scotland to Iceland crossing the Rockall Trough, Hatton-Rockall Basin and Iceland Basin. With 61 full-depth stations at a horizontal resolution of 10 to 50 km, the EEL samples the upper limb of the Atlantic Meridional Overturning Circulation flowing across the Iceland-Scotland Ridge into the Nordic Seas. The Rockall Trough has been sampled nearly four times per year from 1975 to 1996, and the full section annually since 1996. The EEL is an exceptionally long timeseries of deep-ocean temperatures and salinities. This study extends prior work in the Rockall Trough, and examines for the first time 18 year records in the Iceland and Hatton-Rockall Basins. We quantify errors in the timeseries from two sources: observational errors and aliasing. The data quality and annual sampling are suitable for observing interannual to decadal variability because the variability exceeds our error estimates. The upper waters of all 3 basins are cooler/fresher from 1997 to 2001, warmer/more saline 2001 to 2006, and cooler/fresher from 2006 to 2014. A reference level for geostrophic shear is developed heuristically and by comparison with sea-surface altimetry. The mean northward transport in the upper waters is 6.7±3.7 Sv and there is a 6.1±2.5 Sv southward flow below the thermocline. Although the magnitude of the Iceland Basin overturning circulation (4.3±1.9 Sv) is greater than in the Rockall Trough (3.0±3.7 Sv), the variability is greater in the Rockall Trough. We discuss the results in the context of our understanding of drivers of variability. This article is protected by copyright. All rights reserved.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Observed interannual variability of the Atlantic meridional overturning circulation at 26.5°N (2012)
    Wiley
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    Publication Date: 2012-10-12
    Description: The Atlantic meridional overturning circulation (MOC) plays a critical role in the climate system and is responsible for much of the heat transported by the ocean. A mooring array, nominally at 26°N between the Bahamas and the Canary Islands, deployed in Apr 2004 provides continuous measurements of the strength and variability of this circulation. With seven full years of measurements, we now examine the interannual variability of the MOC. While earlier results highlighted substantial seasonal and shorter timescale variability, there had not been significant interannual variability. The mean MOC from 1 Apr 2004 to the 31 March 2009 was 18.5 Sv with the annual means having a standard deviation of only 1.0 Sv. From 1 April 2009 to 31 March 2010, the annually averaged MOC strength was just 12.8 Sv, representing a 30% decline. This downturn persisted from early 2009 to mid-2010. We show that the cause of the decline was not only an anomalous wind-driven event from Dec 2009–Mar 2010 but also a strengthening of the geostrophic flow. In particular, the southward flow in the top 1100 m intensified, while the deep southward return transport—particularly in the deepest layer from 3000–5000 m—weakened. This rebalancing of the transport from the deep overturning to the upper gyre has implications for the heat transported by the Atlantic.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Variability of Antarctic Bottom Water at 24.5°N in the Atlantic (2011)
    Wiley
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    Publication Date: 2011-11-17
    Description: A recent hydrographic section at 24.5°N in the Atlantic and 6 months of observations from a moored array show that Antarctic Bottom Water (AABW), the densest and deepest water mass in the world oceans, has been warming. While Johnson et al. (2008) showed that northward AABW transport at 24.5°N has been declining from 1981 to 2004, suggesting that the lower cell of the overturning circulation could halt in the near future, estimates from the latest hydrographic section in 2010 indicate a partial recovery of northward AABW transport. From 6 months of temperature and salinity observations at a deep moored array at 24–26°N, we find that short-term variability between April and November 2009 is of the same magnitude as the changes observed from hydrographic sections between 1981 and 2004. These observations highlight the possibility that transport changes estimated from hydrographic sections may be aliased by short-term variability. The observed AABW transport variability affects present estimates of the upper meridional overturning circulation by ±0.4 Sv (1 Sv = 106 m3 s−1).
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Vertical structure of eddies and Rossby waves and their effect on the Atlantic meridional overturning circulation at 26.5°N (2014)
    Wiley
    Details
    Publication Date: 2014-09-05
    Description: The meridional overturning circulation (MOC) at 26.5°N in the Atlantic has a standard deviation of 4.9 Sv and contains large fluctuations at subannual periods. The geostrophic component of the MOC is believed to be influenced on subannual timescales by eddies and Rossby waves. To quantify this effect, the vertical structure and surface characteristics of westward propagating signals are studied using altimetric data and full-depth mooring measurements from the RAPID array at 26.5°N. Westward propagating features are observed in the western North Atlantic in both datasets and have periods of 80-250 days in the first baroclinic mode. These features are still observed by the RAPID moorings 20 km offshore of the western boundary. The western boundary also exhibits deep variability characterized by enhanced energy in higher baroclinic modes. The effect of eddies and Rossby waves on the geostrophic transport is quantified by representing their vertical structure with the first baroclinic mode. In total, 42% of the variance of the transbasin thermocline transport inferred from geostrophic calculations at 26.5°N can be attributed to first mode variability, which is associated with eddies and Rossby waves at periods of 80-250 days. The standard deviation of the transbasin thermocline transport due to eddies and Rossby waves is estimated to be 2.6 Sv.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Wild pollinators enhance fruit set of crops regardless of honey bee abundance (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-03-02
    Description: The diversity and abundance of wild insect pollinators have declined in many agricultural landscapes. Whether such declines reduce crop yields, or are mitigated by managed pollinators such as honey bees, is unclear. We found universally positive associations of fruit set with flower visitation by wild insects in 41 crop systems worldwide. In contrast, fruit set increased significantly with flower visitation by honey bees in only 14% of the systems surveyed. Overall, wild insects pollinated crops more effectively; an increase in wild insect visitation enhanced fruit set by twice as much as an equivalent increase in honey bee visitation. Visitation by wild insects and honey bees promoted fruit set independently, so pollination by managed honey bees supplemented, rather than substituted for, pollination by wild insects. Our results suggest that new practices for integrated management of both honey bees and diverse wild insect assemblages will enhance global crop yields.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Garibaldi, Lucas A -- Steffan-Dewenter, Ingolf -- Winfree, Rachael -- Aizen, Marcelo A -- Bommarco, Riccardo -- Cunningham, Saul A -- Kremen, Claire -- Carvalheiro, Luisa G -- Harder, Lawrence D -- Afik, Ohad -- Bartomeus, Ignasi -- Benjamin, Faye -- Boreux, Virginie -- Cariveau, Daniel -- Chacoff, Natacha P -- Dudenhoffer, Jan H -- Freitas, Breno M -- Ghazoul, Jaboury -- Greenleaf, Sarah -- Hipolito, Juliana -- Holzschuh, Andrea -- Howlett, Brad -- Isaacs, Rufus -- Javorek, Steven K -- Kennedy, Christina M -- Krewenka, Kristin M -- Krishnan, Smitha -- Mandelik, Yael -- Mayfield, Margaret M -- Motzke, Iris -- Munyuli, Theodore -- Nault, Brian A -- Otieno, Mark -- Petersen, Jessica -- Pisanty, Gideon -- Potts, Simon G -- Rader, Romina -- Ricketts, Taylor H -- Rundlof, Maj -- Seymour, Colleen L -- Schuepp, Christof -- Szentgyorgyi, Hajnalka -- Taki, Hisatomo -- Tscharntke, Teja -- Vergara, Carlos H -- Viana, Blandina F -- Wanger, Thomas C -- Westphal, Catrin -- Williams, Neal -- Klein, Alexandra M -- New York, N.Y. -- Science. 2013 Mar 29;339(6127):1608-11. doi: 10.1126/science.1230200. Epub 2013 Feb 28.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Sede Andina, Universidad Nacional de Rio Negro (UNRN) and Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), San Carlos de Bariloche, Rio Negro, Argentina. lgaribaldi@unrn.edu.ar〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23449997" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bees/physiology ; Crops, Agricultural/*growth & development ; Flowers/physiology ; Fruit/*growth & development ; Insects/*physiology ; *Pollination
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Observed flow compensation associated with the MOC at 26.5 degrees N in the Atlantic (2007)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2007-08-19
    Description: The Atlantic meridional overturning circulation (MOC), which provides one-quarter of the global meridional heat transport, is composed of a number of separate flow components. How changes in the strength of each of those components may affect that of the others has been unclear because of a lack of adequate data. We continuously observed the MOC at 26.5 degrees N for 1 year using end-point measurements of density, bottom pressure, and ocean currents; cable measurements across the Straits of Florida; and wind stress. The different transport components largely compensate for each other, thus confirming the validity of our monitoring approach. The MOC varied over the period of observation by +/-5.7 x 10(6) cubic meters per second, with density-inferred and wind-driven transports contributing equally to it. We find evidence for depth-independent compensation for the wind-driven surface flow.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kanzow, Torsten -- Cunningham, Stuart A -- Rayner, Darren -- Hirschi, Joel J-M -- Johns, William E -- Baringer, Molly O -- Bryden, Harry L -- Beal, Lisa M -- Meinen, Christopher S -- Marotzke, Jochem -- New York, N.Y. -- Science. 2007 Aug 17;317(5840):938-41.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉National Oceanography Centre, Empress Dock, Southampton, SO14 3ZH, UK. tok@noc.soton.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17702941" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Temporal variability of the Atlantic meridional overturning circulation at 26.5 degrees N (2007)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2007-08-19
    Description: The vigor of Atlantic meridional overturning circulation (MOC) is thought to be vulnerable to global warming, but its short-term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain. We combine continuous measurements of the MOC (beginning in 2004) using the purposefully designed transatlantic Rapid Climate Change array of moored instruments deployed along 26.5 degrees N, with time series of Gulf Stream transport and surface-layer Ekman transport to quantify its intra-annual variability. The year-long average overturning is 18.7 +/- 5.6 sverdrups (Sv) (range: 4.0 to 34.9 Sv, where 1 Sv = a flow of ocean water of 10(6) cubic meters per second). Interannual changes in the overturning can be monitored with a resolution of 1.5 Sv.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cunningham, Stuart A -- Kanzow, Torsten -- Rayner, Darren -- Baringer, Molly O -- Johns, William E -- Marotzke, Jochem -- Longworth, Hannah R -- Grant, Elizabeth M -- Hirschi, Joel J-M -- Beal, Lisa M -- Meinen, Christopher S -- Bryden, Harry L -- New York, N.Y. -- Science. 2007 Aug 17;317(5840):935-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉National Oceanography Centre, Empress Dock, Southampton SO14 3ZH, UK. scu@noc.soton.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17702940" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
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    Eddy Impacts on the Florida Current (2013)
    Wiley
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    Publication Date: 2013-01-11
    Description: [1]  The Gulf Stream in the Atlantic carries warm water northwards and forms both the return closure of the subtropical gyre as well as the upper limb of the meridional overturning circulation. Recent time series recorded east of the Bahamas at 26°N indicate that from May 2009–Apr 2011, in contrast with past observations, the northward flowing Antilles Current covaried with the Gulf Stream in the Florida Straits—the Florida Current—even though the Florida and Antilles Currents are separated by banks and islands spanning 150 km. The peak-to-trough amplitude of transport variations during this period was 15 × 10 6  m 3  S -1 for the Florida Current and 12 × 10 6  m 3  S -1 for the Antilles Current, at timescales of 50 days to a year. From satellite observations, we show that the fluctuations in both the Florida and Antilles Currents between May 2009–Apr 2011 are driven by eddy activity east of the Bahamas. Since the Florida Current time series is a critical time series for thestate of the oceans, and often compared to climate models, this newly identified source of variability needs careful consideration when attributing the variability of the Florida Current to changes in the larger scale circulations (e.g. gyre and overturning) or wind forcing.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Meridional overturning circulation observations in the North Atlantic Ocean (2013)
    In:  EPIC3Bull. Amer. Meteor. Soc., 95(7), pp. 67-69
    Details
    Publication Date: 2016-12-08
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
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    Continuous, array-based estimates of Atlantic Ocean heat transport at 26.5°N (2011)
    American Meteorological Society
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 24 (2011): 2429–2449, doi:10.1175/2010JCLI3997.1.
    Description: Continuous estimates of the oceanic meridional heat transport in the Atlantic are derived from the Rapid Climate Change–Meridional Overturning Circulation (MOC) and Heatflux Array (RAPID–MOCHA) observing system deployed along 26.5°N, for the period from April 2004 to October 2007. The basinwide meridional heat transport (MHT) is derived by combining temperature transports (relative to a common reference) from 1) the Gulf Stream in the Straits of Florida; 2) the western boundary region offshore of Abaco, Bahamas; 3) the Ekman layer [derived from Quick Scatterometer (QuikSCAT) wind stresses]; and 4) the interior ocean monitored by “endpoint” dynamic height moorings. The interior eddy heat transport arising from spatial covariance of the velocity and temperature fields is estimated independently from repeat hydrographic and expendable bathythermograph (XBT) sections and can also be approximated by the array. The results for the 3.5 yr of data thus far available show a mean MHT of 1.33 ± 0.40 PW for 10-day-averaged estimates, on which time scale a basinwide mass balance can be reasonably assumed. The associated MOC strength and variability is 18.5 ± 4.9 Sv (1 Sv ≡ 106 m3 s−1). The continuous heat transport estimates range from a minimum of 0.2 to a maximum of 2.5 PW, with approximately half of the variance caused by Ekman transport changes and half caused by changes in the geostrophic circulation. The data suggest a seasonal cycle of the MHT with a maximum in summer (July–September) and minimum in late winter (March–April), with an annual range of 0.6 PW. A breakdown of the MHT into “overturning” and “gyre” components shows that the overturning component carries 88% of the total heat transport. The overall uncertainty of the annual mean MHT for the 3.5-yr record is 0.14 PW or about 10% of the mean value.
    Description: This research was supported by the U.S. National Science Foundation under Awards OCE0241438 and OCE0728108, by the U.K. RAPID Programme (RAPID Grant NER/T/S/2002/00481), and by the U.S. National Oceanic and Atmospheric Administration, as part of its Western Boundary Time Series Program.
    Keywords: Atlantic Ocean ; Meridonial overturning circulation ; Sea surface temperature ; Transport ; Anomalies
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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