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Salinity is an essential variable for characterizing and understanding the state of the ocean and its role in the climate system. Gridded ocean salinity products, heavily reliant on Argo float measurements since the early 2000s, are widely used in oceanographic and climate research. However, a concerning issue of instrument drift leading to spurious salinity increases ("salty drift") has been identified in a significant number of Argo floats since 2015. This study investigates the potential consequences of this "salty drift" issue on various gridded salinity products. We compare a suite of these products and evaluate their consistency, particularly from 2015 to 2019. Our analysis reveals two major issues with the gridded salinity products after 2015: a sudden increase in global mean salinity and elevated inconsistencies between gridded salinity products. In 2015–2019, the North Indian and North Atlantic Oceans emerged as regions displaying particularly large disagreements between gridded products compared to the prior period, 2010–2014. These findings highlight the substantial impact of the "salty drift" on the reliability of the gridded salinity products. They also underline the critical need for the oceanography community to address these issues to ensure the validity of future ocean and climate studies that utilize gridded salinity products. Plain Language Summary: Salinity is crucial for understanding our planet's oceans and climate. Since 2015, some Argo floats have produced inaccurate salinity measurements that drift to higher values. This study examined several widely used ocean salinity products that were produced primarily based on Argo float measurements to assess how they are affected by the "salty drift" floats. We found that between 2015 and 2019, most of the examined products showed unrealistic increases in global mean salinity and became less consistent than before. Regions most likely affected include the North Indian and North Atlantic Oceans. This "salty drift" issue can impact previous and future global and regional studies using gridded salinity products after 2015 and needs further detailed study by the oceanography and climate communities. Key Points: Multiple gridded salinity products show an unrealistic rise in global mean salinity after 2015, with increases of up to 1.3 × 10−3 per yearThe spread of global mean salinity tripled between 2015 and 2019, translating to an uncertainty of about 1 cm in halosteric sea levelAfter 2015, over 60% of the global ocean, including the North Atlantic and North Indian Oceans, exhibited increased uncertainty in salinity change [ABSTRACT FROM AUTHOR]

Studies of Earth rotation variations generally assume that changes in non-tidal oceanic angular momentum (OAM) manifest the ocean's direct response to atmospheric forces. However, fluctuations in OAM may also arise from chaotic intrinsic ocean processes that originate in local nonlinear (e.g., mesoscale) dynamics and can map into motions and mass variations at basin scales. To examine whether such random mass redistributions effectively excite polar motion, we compute monthly OAM anomalies from a 50-member ensemble of eddy-permitting global ocean/sea-ice simulations that sample intrinsic variability through a perturbation approach on model initial conditions. The resulting OAM (i.e., excitation) functions, χ̂O, are examined for their spread, spectral content, and role in the polar motion excitation budget from 1995 to 2015. We find that intrinsic χ̂O signals are comparable in magnitude to the forced component at all resolved periods except the seasonal band, amounting to ∼46 % of the total oceanic excitation (in terms of standard deviation) on interannual time scales. More than half of the variance in the intrinsic mass term contribution to χ̂O is associated with a single, global mode of random bottom pressure variability, likely generated by nonlinear dynamics in the Drake Passage. Comparisons of observed interannual polar motion excitation against the sum of known surficial mass redistribution effects are sensitive to the representation of intrinsic χ̂O signals: Reductions in the observed excitation variance can be as high as 68 %, or as low as 50 % depending on the choice of the ensemble member. Chaotic oceanic excitation thus emerges as a new factor to consider when interpreting low-frequency polar motion changes in terms of core-mantle interactions or employing forward-modeled OAM estimates for Earth rotation predictions. [ABSTRACT FROM AUTHOR]

Identifying the causes of historical trends in relative sea level--the height of the sea surface relative to Earth's crust--is a prerequisite for predicting future changes. Rates of change along the eastern coast of the USA (the US East Coast) during the past century were spatially variable, and relative sea level rose faster along the Mid-Atlantic Bight than along the South Atlantic Bight and the Gulf of Maine. Past studies suggest that Earth's ongoing response to the last deglaciation.sup.1-5, surface redistribution of ice and water.sup.5-9 and changes in ocean circulation.sup.9-13 contributed considerably to this large-scale spatial pattern. Here we analyse instrumental data.sup.14,15 and proxy reconstructions.sup.4,12 using probabilistic methods.sup.16-18 to show that vertical motions of Earth's crust exerted the dominant control on regional spatial differences in relative sea-level trends along the US East Coast during 1900-2017, explaining most of the large-scale spatial variance. Rates of coastal subsidence caused by ongoing relaxation of the peripheral forebulge associated with the last deglaciation are strongest near North Carolina, Maryland and Virginia. Such structure indicates that Earth's elastic lithosphere is thicker than has been assumed in other models.sup.19-22. We also find a substantial coastal gradient in relative sea-level trends over this period that is unrelated to deglaciation and suggests contributions from twentieth-century redistribution of ice and water. Our results indicate that the majority of large-scale spatial variation in long-term rates of relative sea-level rise on the US East Coast is due to geological processes that will persist at similar rates for centuries.Vertical motions of Earth's crust had the greatest effect on regional spatial differences in relative sea-level trends along the eastern coast of the USA during 1900-2017, explaining most of the large-scale spatial variance in regional rates of sea-level rise., Author(s): Christopher G. Piecuch [sup.1] , Peter Huybers [sup.2] , Carling C. Hay [sup.3] , Andrew C. Kemp [sup.4] , Christopher M. Little [sup.5] , Jerry X. Mitrovica [sup.2] , [...]

Interannual sea‐level variations between the United States (U.S.) Northeast and Southeast Coasts separated by Cape Hatteras are significantly less correlated than those within their respective sectors, but the cause is poorly understood. Here we investigate atmospheric forcing mechanisms that affect the interannual sea‐level co‐variability between these two sectors using an adjoint reconstruction and decomposition approach in the framework of Estimating the Circulation and Climate of the Ocean (ECCO) ocean state estimate. We compare modeled and observed sea‐level changes at representative locations in each sector: Nantucket Island, Massachusetts for the Northeast and Charleston, South Carolina for the Southeast. The adjoint reconstruction and decomposition approach used in this work allows for identification and quantification of the causal mechanisms responsible for observed coastal sea‐level variability. Coherent sea‐level variations in Nantucket and Charleston arise from nearshore wind stress anomalies north of Cape Hatteras and buoyancy forcing, especially from the subpolar North Atlantic, while offshore wind stress anomalies, in contrast, reduce co‐variability. Offshore wind stress contributes much more to interannual sea‐level variation at Charleston than at Nantucket, causing incoherent sea level variations between the two locations. Buoyancy forcing anomalies south of Charleston, including over the Florida shelf, the Gulf of Mexico, and the Caribbean Sea, also reduce co‐variability because they induce sea‐level responses at Charleston but not Nantucket. However, the relative impact of buoyancy forcing on interannual sea‐level co‐variability between the two sectors is much smaller than that of offshore wind stress. Plain Language Summary: The magnitude of year‐to‐year sea‐level variations along the East Coast of the United States (U.S.) can be comparable to that of global mean sea‐level rise over a few decades. These year‐to‐year sea‐level variations contribute to more frequent nuisance floods that affect coastal communities. Year‐to‐year sea‐level variations between the U.S. Northeast and Southeast Coasts separated by Cape Hatteras are significantly less correlated than those within the respective sectors. Understanding causal mechanisms affecting the coherence of year‐to‐year sea‐level variations in the two sectors would help improve sea‐level predictions. Our study attributes year‐to‐year sea‐level variations at Charleston and Nantucket, proxy locations for the U.S. Southeast and Northeast Coasts, to wind and buoyancy forcing (air‐sea heat exchange and precipitation/evaporation at sea surface that both affect seawater buoyancy). We find that nearshore winds north of Cape Hatteras and buoyancy forcing both cause coherent year‐to‐year sea‐level variations between Nantucket and Charleston. Offshore winds affect much more year‐to‐year sea‐level variation at Charleston than that at Nantucket. Offshore winds are the major factor causing less correlated year‐to‐year sea‐level variations between Nantucket and Charleston. Warming/cooling of water south of Charleston affects sea‐level variations at Charleston, but not at Nantucket. However, this effect is smaller than that of the offshore wind. Key Points: Nearshore winds north of Cape Hatteras and buoyancy forcing cause coherent interannual sea‐level variations between Nantucket and CharlestonOffshore winds contribute much more to interannual sea‐level variation at Charleston than to that at NantucketOffshore winds are the major factor causing incoherent interannual sea‐level variations between Nantucket and Charleston [ABSTRACT FROM AUTHOR]