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Sea surface salinity (SSS) anomalies and near-surface thermohaline stratification are key parameters to improve our understanding of sea ice retreat and formation in polar regions. Since 2010, the remote sensing salinity missions ESA Soil Moisture Ocean Salinity (SMOS) and NASA Soil Moisture Active Passive (SMAP) offer unprecedented SSS observations globally (SSSSMOS and SSSSMAP, respectively). In this study, we compare these observations with in situ salinity observations (SSSin‐situ) made during the NASA salinity field campaign Salinity and Stratification at Sea Ice Edge (SASSIE) during the fall of 2022. The SASSIE SSSin‐situ were collected by nine different platforms: Castaway and Underway conductivity–temperature–depth (CTD), Wave Gliders, Thermosalinograph, Snake salinity, Surface Wave Instrument Float with Tracking (SWIFT) drifters, Upper Temperature of the Polar Oceans (UpTempO) buoys, Jet Surface Salinity Profiler (Jet-SSP), and Autonomous Lagrangian Thermometric Observer (ALTO) and Air-Launched Autonomous Micro Observer (ALAMO) profilers. Because satellite SSS retrievals are impacted by land and sea ice contaminations, cold temperatures, and surface roughness, mean differences, root-mean-square difference (RMSD), and standard deviation (STD) between satellite SSS and SSSin‐situ are examined as a function of distance from the coast and sea ice edge, sea surface temperature (SST), and wind speed. We find that SSSSMOS and SSSSMAP are well correlated (0.66 and 0.78, respectively) with similar RMSD when compared with SSSin‐situ. Close to the coast (0–150 km), SSSSMAP compares better with SSSin‐situ with RMSD (<2 g kg−1) lower than that from SSSSMOS. Near the sea ice edge (0–150 km), SSSSMOS compares better with SSSin‐situ with RMSD (<2.5 g kg−1) lower than that from SSSSMAP. In cold water (SST < 1.5°C) and low wind speed conditions (<7 m s−1), both SSSSMOS and SSSSMAP are consistent with each other. The RMSD between SSSSMAP and SSSin‐situ decreases considerably (<1 g kg−1) when SST > 1.5°C, while the RMSD between SSSSMOS and SSSin‐situ shows less dependence on SST.
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Projections of physical conditions in the Gulf of Maine in 2050
The Gulf of Maine (GoM) is currently experiencing its warmest period in the instrumental record. Two high-resolution numerical ocean models were used to downscale global climate projections to produce four estimates of ocean physical properties in the GoM in 2050 for the “business as usual” carbon emission scenario. All simulations project increases in the GoM mean sea surface temperature (of 1.1 °C–2.4 °C) and bottom temperature (of 1.5 °C–2.1 °C). In terms of mean vertical structure, all simulations project temperature increases throughout the water column (surface-to-bottom changes of 0.2 °C–0.5 °C). The GoM volume-averaged changes in temperature range from 1.5 °C to 2.3 °C. Translated to rates, the sea surface temperature projections are all greater than the observed 100-year rate, with two projections below and two above the observed 1982–2013 rate. Sea surface salinity changes are more variable, with three of four simulations projecting decreases. Bottom salinity changes vary spatially and between projections, with three simulations projecting varying increases in deeper waters but decreases in shallower zones and one simulation projecting a salinity increase in all bottom waters. In terms of mean vertical structure, salinity structure varies, with two simulations projecting surface decreases that switch sign with depth and two projecting increases throughout the (subsurface) water column. Three simulations show a difference between coastal and deeper waters whereby the coastal zone is projected to be systematically fresher than deeper waters, by as much as 0.2 g kg–1. Stratification, 50 m to surface, is projected to increase in all simulations, with rates ranging from 0.003 to 0.006 kg m–4 century–1 which are lower than the observed change on the Scotian Shelf. The results from these simulations can be used to assess potential acidification and ecosystem changes in the GoM.
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- Award ID(s):
- 1851866
- PAR ID:
- 10320676
- Date Published:
- Journal Name:
- Elementa: Science of the Anthropocene
- Volume:
- 9
- Issue:
- 1
- ISSN:
- 2325-1026
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1525/elementa.2020.20.00055
