Dra. María del Carmen Heras Sánchez Sea-surface temperature spatiotemporal analysis for the Gulf of California, 1998-2015: regime change simulation Dra. María del Carmen Heras Sánchez Cd. Obregón, Sonora, a 25 de Junio de 2018

Mexico / Universidad de Sonora

The Gulf of California Is a semi-closed marginal sea characterized by a series of basins with differing depths and the Great Islands region. Was formed around 5.3 M years ago. Is one of the five most diverse and productive seas in the world, inhabited by more tan 8,000 marine animal species.

Sea Surface Temperature The Gulf of California has been typified as an evaporation basin with a temperature gradient incrementing toward the Gulf’s interior during summer and decreasing during winter, with a net salt and heat gain that is balanced by sea water flux towards the Pacific ocean. The latter being the mechanism that significantly influences the SST’s variability. The Gulf’s climate is characterized by two distinct seasons: a warm season with SST => 25°C, and a cold season with SST temperatures < 25°C. Spatially-wise, the areas around the large islands and the head of the Gulf show the lowest SST temperatures and the lowest variability in any given year. Interannual SST variability is related to ENSO events. Oceanographic conditions at the mouth of the Gulf are more sensitive to these inter-annual events.

Sea Surface Temperature Surface circulation exhibit a distinct North American Monsoon system influence. A southward flow along the Sonora and Sinaloa coastline during winter-spring, causing important upwellings. Reversing its direction during summer-autumn but having a lesser impact on the thermal stratification along the Baja California Peninsula. Higgins y Shi (2000)

Study area Area: 237,207 km2 The Gulf of California is on average 200 km wide and has a length of 1500 km. Its natural borders are the arid Mexican states of Sonora and Sinaloa on the east, and the equally arid Baja California Peninsula on the west. Its southern edge directly inter-communicates with the Pacific Ocean, but for this study we considered a hypothetical boundary running from Cabo San Lucas, B.C.S., to Bahía de Banderas, Nayarit.

Data set Spatial resolution: 4 km aprox. SST: Time resolution: Monthly Period: January/1998 – December/2015 Number of files: 216 by timeserie Format: raster .NC (NetCDF), .RST Software: Idrisi 18, TerrSet SST: NOAA/ERDDAP/AVHRR, 2015 Aqua Modis/Ocean Color Web, 2016 MEI: NOAA/ESRL, 2016 X = 274 Y = 240 Z = 216

Spatiotemporal Analysis of SST 28 (± 2.6) °C 23.4 (± 5.7) °C Average: 25.4 (± 1.4) °C. SST of large islands < 22.4 (± 4.9) °C. The Gulf of California’s oceanography has been characterized by the sea Surface temperature (SST) at different spatial and temporal scales with data gathered by remote sensors.

Linear trend: 1.38 °C timeserie, 0.076 °C annual, 0.0064 °C monthly Linear trend of SST Average = 25.4 (± 1.4) °C Linear trend: 1.38 °C timeserie, 0.076 °C annual, 0.0064 °C monthly (Confidende level: 95 %) More than 1.4 °C rise 0.2-0.6 °C rise

Linear trend of SSTA: 1.2 °C Spatiotemporal Analysis of SSTA/MEI (-1) r = 0.64 (p < 0.05, confidence level of 95 %) r > 0.60 r ~ 0.50 Linear trend of SSTA: 1.2 °C MEI: Niños: 35 % Niñas: 26 % MEI < 0.5 °C = 39 % SSTA: Niños: 30 % Niñas: 34 % SSTA < 0.5 °C = 36 %

Seasonal trend analysis of SST Seasonal trend amplitudes of SST, 1998-2015 for the Gulf of California. RGB image compo-site: R=amplitude 0 =annual mean; G=amplitude 1 =annual cycle; B=amplitude 2 = semiannual cycle Theil-Sen estimator, allowed us to eliminate both high-frequency noise and low-frequency variability, such that El Niño or La Niña’s effects would be excluded.

Seasonal trend analysis of SST Nov. 23 09:0 May. 07 10:00 Nov. 27 06:00 May. 22 21:00 15. 5 days 3.91 days January Observed (a) and fitted (b) seasonal curves with 25 °C threshold Summer season’s lengthening and summer and winter intensification A fast and shifted SST seasonal change must impact the distribution, abundance, and development of the different species dwelling in the Gulf.

Seasonal trend analysis of SST Signal homogenization Rising trend in amplitude apparently due to pronounced summer and winter seasons Earlier manifestation of the SST midpoint with respect to the previous year Implies a later onset of SST change during the year Theil-Sen trend: 0.72 °C, 0.04 °C annual, 0.0033 °C monthly (confidence level of 95 %) ꜛ 0.72 °C

Seasonal climatology of the Gulf of California

Seasonal trend analysis of SST Gulf of California, SST seasonal trend analysis, 1998-2015, spatial distribution of SST for annual winter and summer Seasonal trend analysis of SST

Seasonal trend analysis of SST For STA, the series was partitioned in two subperiods: 1998-2006, and 2007-2015. Averages for the monthly SST of the Gulf of California, with isotherms at 0.2°C of equidis-tance: 1998-2006(a) and 2007-2015(b) 10 % ꜛ 1.5 % 8.5 % Temporal profiles for monthly SST of the Gulf of California, with Theil-Sen and Linear trends: 1998-2006(a) and 2007-2015(b)

January 18th, 2019

Thank you! Dra. Carmen Heras