Assessment and exploitation of coastal low resolution mode sea level data from CryoSat-2 on the entrance to the Gulf of California

Abstract

The CryoSat-2 mission (CS2), initially conceived for sea ice measurements, is also useful for sea level monitoring in oceanic and coastal areas. Only specific regions have two high resolution modes (SAR Delay/Doppler and SAR-Interferometric modes), while the rest of the areas are measured in low-resolution mode (LRM). The entrance to the Gulf of California presents this mode of operation. Sea Level Anomalies (SLA) obtained from CS2 are compared with tide gauges at three locations, Cabo San Lucas (CSL) south of the Baja California peninsula, Mazatla´n (MZ) and San Blas (SB) on the continental margin. The comparison shows good agreement between SLAs in CSL and MZ, with standard deviations of the differences (SDD) lower than 0.09 m and Pearson’s correlations higher than 0.7 (95% of confidence level). San Blas is in a complex location and with less data, presenting an SDD greater than 0.13 m and a correlation below 0.55. We present the cross-shore seasonal and interannual variability in CSL and MZ using the CS2 SLA time series from 2011 to 2020. The variability shows the presence of events such as El Nin˜o (2015 to early 2016), La Nin˜a (2011) and the warm event of 2014 (nicknamed ‘‘the Blob”). Additionally, the residual time series of CS2 obtained after extracting the annual, semi-annual and monthly components, shows the East side (at MZ) is more affected by El Niño/La Niña variability while the West side (at CSL) is more influenced by the Blob/El Niño. Estimated long-term SLA trend at both locations are around 3.1 mm/yr, supporting similar findings by previous studies.