Seasonal Variability of Horizontal Gradients in the North Atlantic Large-Scale Thermohaline Frontal Zones

I. G. Shokurova*, N. V. Nikolsky, E. D. Chernyshova

Marine Hydrophysical Institute of RAS, Sevastopol, Russia

* e-mail: igshokurova@mail.ru

Abstract

The paper examines seasonal variability in the spatial distribution and magnitude of horizontal gradients of temperature, salinity and density in large-scale surface frontal zones in the North Atlantic Ocean. Monthly average temperature and salinity data at the 0.5 m horizon from the ORAS5 oceanic reanalysis (1958–2021) are used. High gradients of temperature exceeding 2°C/100 km, those of salinity exceeding 1 PSU/100 km, and those of density exceeding 1 kg·m–3/100 km were observed in the subpolar and temperate regions in fronts along large-scale currents carrying warm salty waters from the southern latitudes (Gulf Stream, North Atlantic Current) and cold waters with low salinity from the Arctic regions (Labrador Current, East Greenland Current). These fronts occur throughout the year. High salinity and density gradients are also observed in the tropical summer in the front at the edge of the Amazon River plume, resulting from seasonal river flow. In these five frontal zones, areas were identified for which quantitative estimates of seasonal variability of gradients are provided. In the subpolar and temperate latitudes, maximum temperature gradients are observed in winter. Warming up of water in the summer season is accompanied by a decrease in gradients. The greatest range of seasonal variability of temperature gradients was noted in the frontal zones of the Gulf Stream and the East Greenland Current. In summer, in the fronts of subpolar regions, salinity gradients increase due to the melting of Arctic and continental ice and an increase in the influx of waters with low salinity. In the frontal zone of the East Greenland Current, as well as at the boundary of the Amazon River plume, the highest range of seasonal changes in salinity and density gradients was noted. In these areas, the contribution of salinity to seasonal changes in density at the ocean surface increases.

Keywords

frontal zone, horizontal gradients, temperature gradient, salinity gradient, density gradient, seasonal variability, Atlantic Ocean

Acknowledgments

The study was carried out under state assignment FNNN-2024-0014 “Fundamental studies of interaction processes in the sea-air system that form the physical state variability of the marine environment at various spatial and temporal scales”.

For citation

Shokurova, I.G., Nikolsky, N.V. and Chernyshova, E.D., 2024. Seasonal Variability of Horizontal Gradients in the North Atlantic Large-Scale Thermohaline Frontal Zones. Ecological Safety of Coastal and Shelf Zones of Sea, (2), pp. 23–38.

References

  1. Fedorov, K.N., 1986. The Physical Nature and Structure of Oceanic Fronts. New York: Springer-Verlag, 333 p.
  2. Belkin, I.M., Cornillon, P.C. and Sherman, K., 2009. Fronts in Large Marine Ecosystems. Progress in Oceanography, 81(1–4), pp. 223–236. https://doi.org/10.1016/j.pocean.2009.04.015
  3. Taylor, J.R. and Ferrari, R., 2011. Ocean Fronts Trigger High Latitude Phytoplankton Blooms. Geophysical Research Letters, 38(23), L23601. https://doi.org/10.1029/2011GL049312
  4. Olson, D.B., 2002. Biophysical Dynamics of Ocean Fronts. In: A. R. Robinson, J. J. McCarthy, B. J. Rotschild, Eds., 2002. The Sea: Ideas and Observations on Progress in the Study of the Seas. Harvard University Press. Vol. 12: Biological-Physical Interactions in the Sea, pp. 187–218.
  5. Yang, K., Meyer, A., Strutton, P.G. and Fischer, A.M., 2023. Global Trends of Fronts and Chlorophyll in a Warming Ocean. Communications Earth & Environment, 4, 489. https://doi.org/10.1038/s43247-023-01160-2
  6. Kida S., Mitsudera, H., Aoki, S., Guo, X., Ito, S., Kobashi, F., Komori, N., Kubokawa, A., Miyama, T. [et al.], 2016. Oceanic Fronts and Jets around Japan: a Review. In: H. Nakamura, A. Isobe, S. Minobe, H. Mitsudera, M. Nonaka, T. Suga, eds., 2016. “Hot Spots” in the Climate System: New Developments in the Extratropical Ocean-Atmosphere Interaction Research. Tokyo: Springer, pp. 1–30. https://doi.org/10.1007/978-4-431-56053-1_1
  7. Cromwell, T. and Reid Jr., J. L., 1956. A Study of Oceanic Fronts1. Tellus, 8(1), pp. 94–101. https://doi.org/10.3402/tellusa.v8i1.8947
  8. Ferrari, R., 2011. A Frontal Challenge for Climate Models. Science, 332(6027), pp. 316–317. https://doi.org/10.1126/science.1203632
  9. Swart, S., du Plessis, M.D., Thompson, A.F., Biddle, L.C., Giddy, I., Linders, T., Mohrmann, M. and Nicholson, S.-A., 2020. Submesoscale Fronts in the Antarctic Marginal Ice Zone and Their Response to Wind Forcing. Geophysical Research Letters, 47(6), e2019GL086649. https://doi.org/10.1029/2019GL086649
  10. Kostianoy, A.G., Ginzburg, A.I., Frankignoulle, M. and Delille, B., 2004. Fronts in the Southern Indian Ocean as Inferred from Satellite Sea Surface Temperature Data. Journal of Marine Systems, 45(1–2), pp. 55–73. https://doi.org/10.1016/j.jmarsys.2003.09.004
  11. Konik, A.A. and Zimin, A.V., 2022. Variability of the Arctic Frontal Zone Characteristics in the Barents and Kara Seas in the First Two Decades of the XXI Century. Physical Oceanography, 29(6), pp. 659–673. https://doi.org/10.22449/1573-160X-2022-6-659-673
  12. Artamonov, Yu.V., Skripaleva, E.A. and Nikolsky, N.V., 2022. Climatic Structure of the Dynamic and Temperature Fronts in the Scotia Sea and the Adjacent Water Areas. Physical Oceanography, 29(2), pp. 117–138. https://doi.org/10.22449/1573-160X-2022-2-117-138
  13. Belkin, I.M., 2021. Remote Sensing of Ocean Fronts in Marine Ecology and Fisheries. Remote Sensing, 13(5), 883. https://doi.org/10.3390/rs13050883
  14. Yu, L., 2015. Sea-Surface Salinity Fronts and Associated Salinity-Minimum Zones in the Tropical Ocean. Journal of Geophysical Research: Oceans, 120(6), pp. 4205–4225. https://doi.org/10.1002/2015JC010790
  15. Kostianoy, A.G., Ginzburg, A.I., Lebedev, S.A., Frankignoulle, M. and Delille, B., 2004. Oceanic Fronts in the Southern Indian Ocean as Inferred from the NOAA SST, TOPEX/Poseidon and ERS-2 Altimetry Data. Gayana (Concepción), 68(2, Suppl.), pp. 333–339. https://dx.doi.org/10.4067/S0717-65382004000300003
  16. Akhtyamova, A.F. and Travkin, V.S., 2023. Investigation of Frontal Zones in the Norwegian Sea. Physical Oceanography, 30(1), pp. 62–77. https://doi.org/10.29039/1573-160X-2023-1-62-77
  17. Galerkin, L.I., Gritsenko, A.M., Panfilova, S.G. and Yampol'skii, A.D., 2002. Seasonal Variations in Horizontal Temperature Gradients of Water in the North Atlantic. Doklady Earth Sciences, 384(4), pp. 473–477.
  18. Miller, P.I., Read, J.F. and Dale, A.C., 2013. Thermal Front Variability along the North Atlantic Current Observed Using Microwave and Infrared Satellite Data. Deep Sea Research Part II: Topical Studies in Oceanography, 98(B), pp. 244–256. https://doi.org/10.1016/j.dsr2.2013.08.014
  19. Kazmin, A.S., 2017. Variability of the Climatic Oceanic Frontal Zones and Its Connection with the Large-Scale Atmospheric Forcing. Progress in Oceanography, 154, pp. 38–48. https://doi.org/10.1016/j.pocean.2017.04.012
  20. Artamonov, Yu.V. and Skripaleva, E.A., 2005. The Structure and Seasonal Variability of the Large-Scale Fronts in the Atlantic Ocean on the Basis of Satellite Data. Issledovaniye Zemli iz Kosmosa, (4), pp. 62–75 (in Russian).
  21. Santos, A.M.P., Kazmin, A.S. and Peliz, A., 2005. Decadal Changes in the Canary Upwelling System as Revealed by Satellite Observations: Their Impact on Productivity. Journal of Marine Research, 63(2), pp. 359–379.
  22. Novikova, I.S. and Bashmachnikov, I.L., 2018. Seasonal and Interannual Dynamics of Frontal Zones in the North Atlantic. In: IO RAS, 2018. Proceedings of the II Russian National Conference “Hydrometeorology and Ecology: Scientific and Educational Achievements and Perspectives”. Saint Petersburg: HIMIZDAT, pp. 496–498 (in Russian).
  23. Zuo, H., Balmaseda, M.A., Tietsche, S., Mogensen, K. and Mayer, M., 2019. The ECMWF Operational Ensemble Reanalysis-Analysis System for Ocean and Sea Ice: a Description of the System and Assessment. Ocean Science, 15(3), pp. 779–808. https://doi.org/10.5194/os-15-779-2019
  24. Seidov, D., Mishonov, A., Reagan, J. and Parsons, R., 2019. Eddy-Resolving in situ Ocean Climatologies of Temperature and Salinity in the Northwest Atlantic Ocean. Journal of Geophysical Research: Oceans, 124(1), pp. 41–58. https://doi.org/10.1029/2018JC014548
  25. Daniault, N., Mercier, H., Lherminier, P., Sarafanov, A., Falina, A., Zunino, P., Pérez, F.F., Ríos, A.F., Ferron, B. [et al.], 2016. The Northern North Atlantic Ocean Mean Circulation in the Early 21st Century. Progress in Oceanography, 146, pp. 142–158. https://doi.org/10.1016/j.pocean.2016.06.007
  26. Liu, Y., Wang, J., Han, G., Lin, X., Yang, G. and Ji, Q., 2022. Spatio-Temporal Analysis of East Greenland Polar Front. Frontiers in Marine Science, 9, 943457. https://doi.org/10.3389/fmars.2022.943457
  27. Kostianoy, A.G., Nihoul, J.C.J. and Rodionov, V.B., 2004. Physical Oceanography of Frontal Zones in the Subarctic Seas. Amsterdam: Elsevier, 2004. 316 p.
  28. Ullman, D.S., Cornillon, P.C. and Shan, Z., 2007. On the Characteristics of Subtropical Fronts in the North Atlantic. Journal of Geophysical Research: Oceans, 112(C1), C01010. https://doi.org/10.1029/2006JC003601
  29. Taylor, A.H. and Stephens J.A., 1998. The North Atlantic Oscillation and the latitude of the Gulf Stream. Tellus A: Dynamic Meteorology and Oceanography, 50(1), pp. 134–142. https://doi.org/10.3402/tellusa.v50i1.14517
  30. Richaud, B., Kwon, Y., Joyce, T.M., Fratantoni, P.S. and Lentz, S.J., 2016. Surface and Bottom Temperature and Salinity Climatology along the Continental Shelf off the Canadian and U.S. East Coasts. Continental Shelf Research, 124, pp. 165–181. https://doi.org/10.1016/j.csr.2016.06.005
  31. Han, G., Lu, Z., Wang, Z., Helbig, J., Chen, N. and de Young, B., 2008. Seasonal Variability of the Labrador Current and Shelf Circulation off Newfoundland. Journal of Geophysical Research: Oceans, 113(C10), C10013. https://doi.org/10.1029/2007JC004376
  32. Grodsky, S.A., Reul, N., Chapron, B., Carton, J. A. and Bryan, F.O., 2017. Interannual Surface Salinity on Northwest Atlantic Shelf. Journal of Geophysical Research: Oceans, 122(5), pp. 3638–3659. https://doi.org/10.1002/2016JC012580
  33. Ohashi, K. and Sheng, J., 2013. Influence of St. Lawrence River Discharge on the Circulation and Hydrography in Canadian Atlantic Waters. Continental Shelf Research, 58, pp. 32–49. https://doi.org/10.1016/j.csr.2013.03.005
  34. Bacon, S., Marshall, A., Holliday, N.P., Aksenov, Y. and Dye, S.R., 2014. Seasonal Variability of the East Greenland Coastal Current. Journal of Geophysical Research: Oceans, 119(6), pp. 3967–3987. https://doi.org/10.1002/2013JC009279
  35. Liang, Y.C., Lo, M.H., Lan, C.W., Seo, H., Ummenhofer, C.C., Yeager, S., Wu, R.J. and Steffen, J.D., 2020. Amplified Seasonal Cycle in Hydroclimate over the Amazon River Basin and Its Plume Region. Nature Communications, 11, 4390. https://doi.org/10.1038/s41467-020-18187-0
  36. Yu, L., Jin, X. and Weller, R.A., 2006. Role of Net Surface Heat Flux in Seasonal Variations of Sea Surface Temperature in the Tropical Atlantic Ocean. Journal of Climate, 19(23), pp. 6153–6169. https://doi.org/10.1175/JCLI3970.1

Full text

English version (PDF)

Russian version (PDF)

We use Yandex Metrics. Read more.

Мы используем Яндекс Метрику. Подробнее.