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WaMoS-II also performed a running average over 20min to minimise the effects of natural variability. Glaciology, 61, All other systems are swell and are ranked based on their energy contents as primary, secondary, and tertiary swell. Ackley, S. F., Stammerjohn, S., Maksym, T., Smith, M., Cassano, J., Guest, P., Tison, J. L., Delille, B., Loose, B., Sedwick, P., DePace, L., Roach, L., and Parno, J.: Sea-ice An ocean gyre is a large system of circular ocean currents formed by global wind patterns and forces created by Earth's rotation. Measurements were assessed for quality control and compared against available satellite observations. In turn, this drawback impacts prediction models, which are impaired by notable biases in the Southern Ocean (see, for example,Yuan,2004; Li etal.,2013; Zieger etal.,2015). Lett., 39, L16606, https://doi.org/10.1029/2012GL052290, 2012.a, Smart, S.M., Fawcett, S.E., Ren, H., Schiebel, R., Tompkins, E.M., Landwehr, S., Volpi, M., Derkani, M.H., Nelli, F., Alberello, A., Toffoli, A., Gysel-Beer, M., Modini, R.L., and Schmale, J.: Sea State and Boundary Layer Stability Limit Sea Spray Aerosol Lifetime over the Southern Ocean, Earth Space Sci. To address the lack of in situ observations and support calibration and validation of satellite sensors and prediction models, an international initiative, organised by the Swiss Polar Institute, led an unprecedented circumnavigation of the Antarctic continent (the Antarctic Circumnavigation Expedition, ACE;Walton and Thomas,2018) during the Austral summer of 20162017. Sci., wind-generated ocean waves, Philos. Significant wave heights reconstructed from ship motion data were validated against freely available satellite observations (Ribal and Young,2019) for the entire ACE voyage (see scatter plot in Fig.B1). The qualitative statement that AMOC has been losing stability in the last century remains true even taking all uncertainties into account, said Niklas Boers, a scientist at the Potsdam Institute for Climate Impact Research in Germany. Remote, 59, 526, INSPEC Accession Number: 20266256, https://doi.org/10.1109/TGRS.2020.2994372, 2020.a, Hessner, K., Reichert, K., Dittmer, J., Borge, J. C.N., and Gnther, H.: Rev. Figure2Examples of sea state conditions: ocean surface during storm conditions (a), sailing through a storm (b), and the marginal ice zone (c). Tech., 13, 34873506, https://doi.org/10.5194/amt-13-3487-2020, 2020a.a, Landwehr, S., Volpi, M., Derkani, M.H., Nelli, F., Alberello, A., Toffoli, A., Gysel-Beer, M., Modini, R.L., and Schmale, J.: Sea State and Boundary Layer Stability Limit Sea Spray Aerosol Lifetime over the Southern Ocean, Earth Space Sci. Circumnavigation Expedition 2017: WaMoS Data, Ver. Antarctic pack ice, J. Geophys. Martinson, D.G. and Wamser, C.: Ice drift and momentum exchange in winter This allows WaMoS-II to acquire a radar image with a spatial resolution of 12m and an angular resolution of 0.9 for every radar rotation (a sample image is reported in Fig.3b). More broadly, it refers to the body of water south of the main landmasses of Africa, Australia, and South America, with a northern limit at approximately 40S (see, for example,Young etal.,2020). Geophys., 10371064, Metal Accumulations in Two Extreme-Environment Amphipods, Hadal - MDPI Fluid Mech., 28, 279321, 1996.a, Meylan, M.H., Bennetts, L.G., and Kohout, A.L.: In situ measurements and Adv., 6, eaay8493, https://doi.org/10.1126/sciadv.aay8493, 2020.a, Thomas, S., Babanin, A.V., Walsh, K. J.E., Stoney, L., and Heil, P.: Effect of Preindustrial-like Aerosols and Their Climate Effects (ACE-SPACE), B. Adv., 6, eaay8493, Thomas, S., Babanin, A.V., Walsh, K. J.E., Stoney, L., and Heil, P.: Effect Res.-Oceans, 125, e2019JC015418, https://doi.org/10.1029/2019JC015418, Under Earths current climate, this aquatic conveyor belt transports warm, salty water from the tropics to the North Atlantic, and then sends colder water back south along the ocean floor. Two of these events were equal to or greater than the P90 for the season (15ms1). technique for the retrieval of near-surface vertical current shear from Soc., 100, 22602283, https://doi.org/10.1175/BAMS-D-18-0187.1, 2019.a, b, c, d, e, f, Schulz, E., Grosenbaugh, M.A., Pender, L., Greenslade, D., and Trull, T.W.: A, 315, 509562, 1985., Dong, S., Gille, S.T., and Sprintall, J.: An assessment of the Southern Ocean mixed layer heat budget, J. https://doi.org/10.1103/PhysRevLett.118.144503, 2017.a, b, Treguier, A.-M. and Klein, P.: Instability of wind-forced inertial Rev. Antarctic pack ice, J. Geophys. Res. https://doi.org/10.1002/2015GL065937, 2015.a, Toffoli, A., Proment, D., Salman, H., Monbaliu, J., Frascoli, F., Dafilis, M., Stramignoni, E., Forza, R., Manfrin, M., and Onorato, M.: Wind Generated Pt. (1996). Data, 6, 115, interaction-induced vertical mixing and its effects in ocean and climate The basic input for extracting sea state features is a sequence of 64 consecutive images, which correspond to a time period of 175s (one complete image is acquired for every full turn of the antenna). Lett., 37, L05603, https://doi.org/10.1029/2009GL041771, 2010.a, b, Toffoli, A., McConochie, J., Ghantous, M., Loffredo, L., and Babanin, A.V.: The sea state monitoring system was calibrated with benchmark sea state records, which were reconstructed from the ship motion. Figure4Time series of significant wave height Hs: benchmark observations derived from ship motion data (red dots) and calibrated records from WaMoS-II (blue solid line). Therefore, its zeroth-order moment (m0) represents a signal-to-noise ratio (SNR) instead of the significant wave height, i.e. and Drivers of Marine Isoprene Concentration across the Southern Ocean, Atmosphere-Basel, 11, 556, https://doi.org/10.3390/atmos11060556, 2020.a, b, Schmale, J., Baccarini, A., Thurnherr, I., Henning, S., Efraim, A., Regayre, Find support for a specific problem in the support section of our website. Between 40 and 60S, the belt where most of Leg1 and Leg3 took place, P50 3.5m, and P90 ranges between 5 and 6m (Fig.5c and d). of Preindustrial-like Aerosols and Their Climate Effects (ACE-SPACE), B. Rogue Waves in an Annular Wave Flume, Phys. Further, Ekman components remain uncertain in the Southern Ocean due to inaccuracies in estimating wind stress from the atmospheric system, adding inconsistencies to benchmark statistics. Examples of collocated wave spectra from WaMoS-II and SAR are presented in Fig.9; mean wind direction is also reported. New study finds world's strongest ocean current speeding up Waves Dataset from SAR, Australian Ocean Data Network. (2020) contains time series of wind speed and direction, current speed and direction, sea state parameters including wave height, period, wavelength and mean direction for total sea, wind sea and swell systems, ship course, position, and speed for each month of the expedition (https://doi.org/10.26179/5e9d038c396f2). of the 11th European Wave and Tidal Energy Conference (EWTEC2015), September2015, Nantes, France, ID: hal-01198800, 2015.. radar based wave and current monitoring system, in: The Ninth International Acting as an interface between the lower atmosphere and the upper ocean, waves entrap and release momentum, heat, moisture, and gases through breaking (Melville,1996; Csanady,2001; Veron,2015) and drive airsea fluxes (e.g.Humphries etal.,2016; Schmale etal.,2019; Thurnherr etal.,2020). This is an exceptionally high value for ocean waves and is normally associated with the formation of rogue waves (Onorato etal.,2009; Toffoli etal.,2010). As a consequence, observations of waves in ice are not available in the present database. Author to whom correspondence should be addressed. FULL STORY The Antarctic Circumpolar Current (ACC), the only ocean current that circumnavigates the planet, is speeding up. Ocean. Day and time of available measurements can be found in the file Available_Measurements_List.txt, which is included in Alberello etal. Above all, intense winds give rise to some of the fiercest waves on the planet (e.gBarbariol etal.,2019; Vichi etal.,2019; Young and Ribal,2019; Young etal.,2020). 'Something weird is going on': search for answers as Antarctic sea ice A satellite view over Antarctica reveals a frozen continent surrounded by icy waters. Ocean. J. Mar. 1661516629, 1996.a, Hatten, H., Seemann, J., Horstmann, J., and Ziemer, F.: Azimuthal dependence of the radar cross section and the spectral background noise of a nautical radar at grazing incidence, Int. ocean waves, Geophys. Ocean. Antarctic sea ice has usually been able to recover in winter. Geosci. The effect of wave-induced turbulence on the ocean mixed layer during Antarctic Circumpolar Current picking up speed | Polarjournal Yet the dangers of even a partial AMOC shutdown mean any indicators of instability are worth investigating, said Stefan Rahmstorf, another oceanographer at the Potsdam Institute who was not involved in the new study. Images that are deemed of low quality are excluded. This work is distributed under, Department of Infrastructure Engineering, The University of Melbourne, 3010, Melbourne, Victoria, Australia, Department of Physics, University of Turin, 10125, Turin, Italy, School of Mathematical Sciences, University of Adelaide, 5005, Adelaide, South Australia, Australia, OceanWaveS GmbH, 21339 Lneburg, Germany, Department of Civil Engineering, University of Cape Town, 7701, Cape Town, South Africa, Independent Scholar, 6021 Wellington, New Zealand, Oceans and Atmosphere, Commonwealth Scientific and Industrial Research Organisation, 3195, Aspendale, Victoria, Australia. 1. Significant wave height Hs follows the wind pattern, underpinning the dominance of wind seas on swell systems. Figure1Map of the ACE voyage divided by legs. In order to be human-readable, please install an RSS reader. and Drivers of Marine Isoprene Concentration across the Southern Ocean, Chapter 4.6 The antarctic circumpolar current system The root-mean squared error (RMSE) is 0.4m, the correlation coefficient (R) is 0.94, and the scatter index (SI) is 0.17. N., Schnaiter, M., Toffoli, A., Derkani, M., Bukowiecki, N., Stratmann, F., state estimation, Ocean Eng., 129, 352362, 2017.a, NietoBorge, J., Hessner, K., and Reichert, K.: Estimation of the significant The spectral peak that satisfies the condition. Ocean. This was most common during Leg2, as the radar was often switched to long range to detect icebergs. The objective of the expedition was to sample concomitant processes in the lower atmosphere, at the ocean surface, and in the upper-ocean layers all around the Antarctic continent in a single season (Rodrguez-Ros etal.,2020; Schmale etal.,2019; Smart etal.,2020; Thurnherr etal.,2020). The hadal zone and Antarctic Ocean are two of the least-explored habitats. Ocean. Res. Here we use a 15 year time series of SSH observations to determine the circumpolar structure and distribution of the ACC fronts. Here, we analyzed the metal accumulations of two amphipod species, Eurythenes gryllus, from the Mariana Trench (6040 m, 11.36N, 142.41E) in the West Pacific Ocean, and Pseudorchomene plebs, from the Ross Sea (600 m, 77.12 S, 167,67 E) in . Offshore and Polar Engineers, Brest, France, May 1999, ID: ISOPE-I-99-246, 1999.a, Ribal, A. and Young, I.R.: 33 years of globally calibrated wave height and Although the Antarctic Circumpolar Current (ACC) is the longest and the strongest oceanic current on the Earth and is the primary means of inter-basin exchange, it remains one of the most poorly understood components of global ocean circulation. Lett., 42, 85478554, , 2019), which mixes warm waters descending from the Atlantic, Indian, and Pacific oceans with northward cold streams from the Antarctic. The marine radar forms images of the surrounding area based on the backscatter of radar beams. A, 374, 20150201, 2016., Reichert, K., Hessner, K., NietoBorge, J.C., and Dittmer, J.: WaMoS-II: A FigureB1Satellite observations versus significant wave height reconstructed from ship motion. An overview of ship motion to sea state conversion (the wave buoy analogy) can be found in for exampleNielsen (2017). marine X-band radar images, J. Geophys. RMS of Sea Height Go. marine X-band radar images, J. Geophys. Canada, 2010.a, Martinson, D.G. and Wamser, C.: Ice drift and momentum exchange in winter Pt. . Current direction is generally in better agreement with satellite observations than speed (see Fig.12a and b). Apart from a region east of Argentina, where the South American continent induces a shadowing effect, wind speed is fairly uniform throughout the ocean: P50 varies between 10 and 12ms1, while P90 ranges between 15 and 18ms1 (see Fig.5a and b). Explainer: how the Antarctic Circumpolar Current - The Conversation Figure12Surface current velocities along the ACE voyage: WaMoS-II (a) and space-borne altimeter sensors (b). The majority of low-quality images were acquired in the marginal ice zone (i.e. 8: 1515. Wadhams, P.: The Seasonal Ice Zone, Springer US, Boston, MA. Break dancing in the Paris Games: Celebrating a culture or co-opting it? Onorato, M., and Toffoli, A.: Drift of Pancake Ice Floes in the Winter Tech., 21, 12911300, 2004.. interaction-induced vertical mixing and its effects in ocean and climate Understanding the Seasonal Cycle of Antarctic Sea Ice Extent in the Context Radar imaging effects like tilt modulation, which refers to changes in the effective incidence angle along the long-wave slope, and shadowing, which is caused by the highest waves in the image, contribute to an inaccurate form of the resulting spectral density function, shifting energy towards high wave numbers (NietoBorge etal.,2004). spreading of ocean wave spectra in the marginal ice zone, J. Fluid Alberello, A., Bennetts, L., and Toffoli, A.: Antarctic Circumnavigation The wave spectrum E(f,) was sampled at 175s, assuming no gaps or corrupted images occur during the sampling of 64 consecutive radar images. Lett., 102, Park, Y.-H., Park, T., Kim, T.-W., Lee, S.-H., Hong, C.-S., Lee, J.-H., Rio, Antartic Circumpolar Current. Fluid Mech., 47, 507538, 2015., Vichi, M., Eayrs, C., Alberello, A., Bekker, A., Bennetts, L., Holland, D., Orbital- and millennial-scale Antarctic Circumpolar Current - Nature In its standard output format, WaMoS-II archives the wave spectrum as a function of wave frequency, f=/2, and direction, E(f,); the change in variables from wave numbers to frequencydirection satisfies the dispersion relation in Eq.(1). Excluding the regions south of the 60th parallel, which undergo a strong seasonal sea ice cycle (Eayrs etal.,2019), the Southern Ocean is normally characterised by weak seasonal variability (Young etal.,2020). Conf. . This region is dominated by strong westerly winds, the notorious roaring forties, furious fifties, and screaming sixties (Lundy,2010). Tech., 18, 277293, 2001.a, Hasselmann, S., Brning, C., Hasselmann, K., and Heimbach, P.: An improved algorithm for the retrieval of ocean wave spectra from synthetic aperture radar image spectra, J. Geophys. The current is in a region of the world with intense winds and wave action. There is an evident shadowing effect east of the Drake Passage, due to a combination of lower wind speed and a reduction of fetches. Stansberg, C., Tamura, H., and Trulsen, K.: Statistical properties of (2019), Lund etal. Ocean Gyre - National Geographic Society Toffoli, A., Babanin, A., Onorato, M., and Waseda, T.: Maximum Steepness of Figure11Scatter plot of WaMoS-II surface current speeds against observations derived from satellite sensors. L., Bolas, C., Hartmann, M., Welti, A., Lehtipalo, K., Aemisegger, F., Open Arch., 15, Li, M., Liu, J., Wang, Z., Wang, H., Zhang, Z., Zhang, L., and Yang, Q.: WaMoS-II automatically assesses the reliability of images through an internal quality control protocol (seeHessner etal.,2019), which evaluates backscatter intensity, number of sea clutters, and stability of ship motion among other parameters (we remark that tilting and shadowing effects are compensated for independently using the MTF and do not contribute to quality control). Observations of the Antarctic Circumpolar Current over the Udintsev Fracture Zone, the narrowest choke point in the Southern Ocean, J. Geophys. Martnez-Garca, A., Stirnimann, L., Roychoudhury, A., Haug, G.H., and Sigman, D.M.: The Nitrogen Isotopic Composition of Tissue and Res.-Oceans, 90, 10491059, Oceanic currents are driven by three main factors: 2023, 11, 1515. LA and SK provided SAR spectra. South Atlantic Gyre - Wikipedia The latter, however, does not coincide with the wave energy spectrum, because it represents the intensity of the radar backscatter rather than the amplitude of the water surface elevation (NietoBorge etal.,1999; Hessner etal.,2002). Knowledge about human impacts on these two extreme environments is limited. methods, instructions or products referred to in the content. reliability of surface current measurements by X-Band marine radar, Remote Rogue Waves in an Annular Wave Flume, Phys. Findings: IODP Report Blogs and educational resources developed during this expedition The purpose of the Dynamics of Pacific Antarctic Circumpolar Current (DYNAPACC) expedition is to better understand the interactions between the atmosphere, ocean, and frozen waters around the continent of Antarctica. directional wave spectra, J. Atmos.