Abstract
In addition to the sea level (SL) change, or anomaly (SLA), due to ocean thermal expansion, total steric SLA (SSLA, all change to the existing volume of ocean water) is also affected by ocean salinity variation. Less attention, however, has been paid to this halosteric effect, due to the global dominance of thermosteric SLA (TSLA) and the scarcity of salinity measurements. Here, we analyze halosteric SLA (HSLA) since 2005, when Argo data reached near-global ocean coverage, based on several observational products. We find that, on global average, the halosteric component contributes negatively by ~5.8% to SSLA during the 2005–2015 period, and reveals a modest correlation (~0.38) with ENSO on the inter-annual scale. Vertically, the global ocean was saltier in the upper 200-m and fresher within 200 to 600-m since 2005, while the change below 600-m was not significantly different from zero. The upper 200-m changes dominate the HSLA, suggesting the importance of surface fresh water flux forcing; meanwhile, the ocean dynamic might also play a role. The inconsistent pattern of salinity trend between upper 200-m and 200 to 600-m implies the importance of ocean dynamics. Our analysis suggests that local salinity changes cannot be neglected, and can even play a more important role in SSLA than the thermosteric component in some regions, such as the Tropical/North Pacific Ocean, the Southern Ocean, and the North Atlantic Ocean. This study highlights the need to better reconstruct historical salinity datasets, to better monitor the past SSLA changes. Also, it is important to understand the mechanisms (ocean dynamics vs. surface flux) related to regional ocean salinity changes.
Highlights
The Sea level change, hereafter referred to as sea level anomaly (SLA) to denote change from the long-term mean, is one of the central climate metrics, a measure and consequence of the ongoing global warming
SLA is crucial for the coastal areas that are expected to become more vulnerable to land loss
The trend of steric sea level anomaly (SSLA) is within 2005–2015 ranges from 0.83 to 0.97 mm/yr for different products (Table 1), with an ensemble mean of 0.86 ± 0.18 mm/yr
Summary
The Sea level change, hereafter referred to as sea level anomaly (SLA) to denote change from the long-term mean, is one of the central climate metrics, a measure and consequence of the ongoing global warming. SLA is crucial for the coastal areas that are expected to become more vulnerable to land loss. Monitoring present SLA, understanding its cause, and projecting future SLA are important topics in climate researches. The total SLA can be divided into steric sea level and barystatic sea level components. Total steric sea level anomaly (SSLA) represents all SLA, due to ocean volume increase or decrease (caused by temperature and salinity variations) [1]. Temperature change causes “thermosteric” SLA (TSLA, thermal expansion/contraction of ocean volume), while salinity change leads to “halosteric”
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
