Trends in the Interannual Variability of Salinity Field in the Upper 1000-Meter Layer of the Northeastern Pacific Ocean under Conditions of Modern Global Warming

I. D. Rostov, E. V. Dmitrieva

V. I. Il’ichev Pacific Oceanological Institute, Far Eastern Branch of RAS, Vladivostok, Russian Federation



Purpose. The study is purposed at determining the trends and the regional features of interannual changes in salinity and salt content in the upper 1000-m layer of the extratropical zone in the northeastern Pacific Ocean, and at analyzing their possible cause-and-effect relations with large-scale and regional processes in the ocean and the atmosphere over the last two decades of the current period of global warming.

Methods and Results. The NOAA climate data sets including the GODAS oceanographic data assimilation system in the nodes of a regular grid, as well as the data on the amount of atmospheric precipitation and the series of climate indices were used in the study. The monthly average ERA5 reanalysis data on precipitation and evaporation from the underlying surface were also applied. The methods of cluster, correlation and regression analysis, as well as the apparatus of empirical orthogonal functions were involved. The conducted research resulted in identifying the regional spatial and temporal features of the changes in salinity and salt content in the upper 1000-m water column of the study area under conditions of the current warming phase accompanied by the intensification of global and local hydrological cycles. The quantitative characteristics of the noted trends and their statistical significance were assessed.

Conclusions. The spatial distribution of evaporation-precipitation (E-P) difference trends demonstrates a predominant evaporation pattern over most of the water area that differs from the global trends in a hydrological cycle in the middle and high latitudes of the Northern Hemisphere, especially over the previous period. In general, a statistically significant positive trend in salt content was observed in the upper 1000 m of the water column in the northern area, whereas in other regions and on the average over the whole water area, small statistically insignificant negative trends were noted in the above-mentioned layer. The correlation relations between the changes in average annual salinity and salt content values, on the one hand, and different large-scale regional processes and climate variables, on the other hand, are most manifested through the following parameters: climate indices NPGO, IPO, PDO and AD, the first mode of EOF of fluctuations in the PC1 values of evaporation-precipitation (E-P) difference, and the second mode of EOF of anomaly of the isobaric surface AT500 geopotential.


northeastern part of the Pacific Ocean, extratropical zone, climate changes, hydrological cycle, salinity, salt content, trends, regional features, climate indices, correlations


The study was carried out within the framework of the theme of state assignment of POI FEB of RAS No. 121021700346-7 “Study of the main processes which determine state and variability of oceanological characteristics of the marginal seas of Asia and the adjacent regions of the Pacific and Indian oceans”. The authors are grateful to the developers for the opportunity to use the climatic data posted on the NOAA websites.

Original russian text

Original Russian Text © I. D. Rostov, E. V. Dmitrieva, 2024, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 40, Iss. 3, pp. 386–401 (2024)

For citation

Rostov, I.D. and Dmitrieva, E.V., 2024. Trends in the Interannual Variability of Salinity Field in the Upper 1000-Meter Layer of the Northeastern Pacific Ocean under Conditions of Modern Global Warming. Physical Oceanography, 31(3), pp. 350-363.


  1. Lagerloef, G., Schmitt, R., Schanze, J. and Kao, H.-Y., 2010. The Ocean and the Global Water Cycle. Oceanography, 23(4), pp. 82-93.
  2. Zika, J.D., Skliris, N., Nurser, A.J.G., Josey, S.A., Mudryk, L., Laliberté, F. and Marsh, R., 2015. Maintenance and Broadening of the Ocean’s Salinity Distribution by the Water Cycle. Journal of Climate, 28(24), pp. 9550-9560.
  3. Yu, L., Josey, S.A., Bingham, F.M. and Lee, T., 2020. Intensification of the Global Water Cycle and Evidence from Ocean Salinity: A Synthesis Review. Annals of the New York Academy of Science, 1472(1), pp. 76-94.
  4. Liu, M., Vecchi, G., Soden, B., Yang, W. and Zhang, B., 2021. Enhanced Hydrological Cycle Increases Ocean Heat Uptake and Moderates Transient Climate Change. Nature Climate Change, 11(10), pp. 848-853.
  5. Liu, Y., Cheng, L., Pan, Y., Abraham, J., Zhang, B., Zhu, J. and Song, J., 2022. Climatological Seasonal Variation of the Upper Ocean Salinity. International Journal of Climatology, 42(6), pp. 3477-3498.
  6. Durack, P.J. and Wijffels, S.E., 2010. Fifty-Year Trends in Global Ocean Salinities and Their Relationship to Broad-Scale Warming. Journal of Climate, 23(16), pp. 4342-4362.
  7. Helm, K.P., Bindoff, N.L. and Church, J.A., 2010. Changes in the Global Hydrological-Cycle Inferred from Ocean Salinity. Geophysical Research Letters, 37(18), L18701.
  8. Yu, L., 2021. A Global Relationship between the Ocean Water Cycle and Near-Surface Salinity. Journal of Geophysical Research, 116(C10), C10025.
  9. Li, G., Zhang, Y., Xiao, J., Song, X., Abraham, J., Cheng, L. and Zhu, J., 2019. Examining the Salinity Change in the Upper Pacific Ocean during the Argo Period. Climate Dynamics, 53(9–10), pp. 6055-6074.
  10. Skliris, N., Marsh, R., Josey, S.A., Good, S.A., Liu, C. and Allan, R.P., 2014. Salinity Changes in the World Ocean since 1950 in Relation to Changing Surface Freshwater Fluxes. Climate Dynamics, 43(3–4), pp. 709-736.
  11. Durack, P.J., 2015. Ocean Salinity and the Global Water Cycle. Oceanography, 28(1), pp. 20-31.
  12. Cheng, L., Trenberth, K.E., Gruber, N., Abraham, J.P., Fasullo, J.T., Li, G., Mann, M.E., Zhao, X. and Zhu, J., 2020. Improved Estimates of Changes in Upper Ocean Salinity and the Hydrological Cycle. Journal of Climate, 33(23), pp. 10357-10381.
  13. Cravatte, S., Delcroix, T., Zhang, D., McPhaden, M. and Leloup, J., 2009. Observed Freshening and Warming of the Western Pacific Warm Pool. Climate Dynamics, 33(4), pp. 565-589.
  14. Friedman, A.R., Reverdin, G., Khodri, M. and Gastineau, G., 2017. A New Record of Atlantic Sea Surface Salinity from 1896 to 2013 Reveals the Signatures of Climate Variability and Long-Term Trends. Geophysical Research Letters, 44(4), pp. 1866-1876.
  15. Shi, H. and Du, L., 2021. The Unexpected Salinity Trend Shifts in Upper Tropical Pacific Ocean under the Global Hydrological Cycle Framework. In: EGU, 2021. EGU General Assembly 2021. Gottingen, 2021. EGU21-14698.
  16. Rostov, I.D. and Dmitrieva, E.V., 2021. Regional Features of Interannual Variations in Water Temperature in the Subarctic Pacific. Russian Meteorology and Hydrology, 46(2), pp. 106-114.
  17. Loeb, N.G., Thorsen, T.J., Norris, J.R., Wang, H. and Su, W., 2018. Changes in Earth’s Energy Budget during and after the “Pause” in Global Warming: An Observational Perspective. Climate, 6(3), 62.
  18. Bond, N.A., Cronin, M.F., Freeland, H. and Mantua, N., 2015. Causes and Impacts of the 2014 Warm Anomaly in the NE Pacific. Geophysical Research Letters, 42(9), pp. 3414-3420.
  19. Amaya, D.J., Miller, A.J., Xie, S.-P. and Kosaka, Y., 2020. Physical Drivers of the Summer 2019 North Pacific Marine Heatwave. Nature Communications, 11, 1903.
  20. Rostov, I.D. and Dmitrieva, E.V., 2024. Interannual Salinity Changes in the Upper 1000-Meter Layer of Extratropical Zone in the Northwestern Pacific Ocean under Conditions of the Intensification of Global Hydrological Cycle. Physical Oceanography, 31(2), pp. 194-207.
  21. Corbett, C.M., Subrahmanyam, B. and Giese, B.S., 2017. A Comparison of Sea Surface Salinity in the Equatorial Pacific Ocean during the 1997–1998, 2012–2013, and 2014–2015 ENSO Events. Climate Dynamics, 49(9–10), pp. 3513-3526.
  22. Favorite, F., Dodimead, A.J. and Nasu, K., 1976. Oceanography of the Subarctic Pacific Region, 1960-71. Tokyo, Japan: Kenkyusha Printing Company, 187 p.
  23. Kuroda, H., Suyama, S., Miyamoto, H., Setou, T. and Nakanowatari, T., 2021. Interdecadal Variability of the Western Subarctic Gyre in the North Pacific Ocean. Deep Sea Research Part I: Oceanographic Research Papers, 169, 103461.
  24. Rostov, I.D., Dmitrieva, E.V. and Rudykh, N.I., 2023. Trends and Regional Features of Variability of the Northeast Pacific Ocean Thermal Conditions North of 30°N over the Last Four Decades. Physical Oceanography, 30(4), pp. 410-427.

Download the article (PDF)