Warming and salinity changes of the upper ocean Caribbean through-flow since 1960

Area of Science:

• Oceanography
• Climate Science
• Earth System Science

Background:

• The Caribbean through-flow (CTF) is a critical oceanic pathway connecting the Atlantic and Pacific Oceans.
• It plays a significant role in regulating heat and salt transport, influencing major climate systems like the North Atlantic Subtropical Gyre (NASTG) and Atlantic Meridional Overturning Circulation (AMOC).

Purpose of the Study:

• To investigate changes in the upper ocean water mass properties of the CTF since 1960.
• To understand the implications of these changes for broader climate dynamics and ocean circulation.

Main Methods:

• Analysis of historical oceanographic data from 1960 onwards.
• Quantification of trends in temperature, salinity, and water mass stability within the CTF.

Main Results:

• Observed significant upper ocean changes in the CTF: subsurface warming (~0.2°C decade⁻¹), surface freshening (~0.13 g kg⁻¹ decade⁻¹), and subsurface salinification (~0.05 g kg⁻¹ decade⁻¹).
• Temperature and stability increases in the upper 0-200m are substantially larger than global averages, nearly 3 and 20 times, respectively.
• These alterations in the CTF are impacting water mass formation in the NASTG, with indirect effects on the AMOC.

Conclusions:

• The CTF acts as a crucial bottleneck for climatically significant water masses.
• The observed changes in the CTF have far-reaching implications for tropical cyclones, sea level rise, and marine ecosystems.
• Sustained subsurface oceanographic observations in the CTF are essential for monitoring and understanding its role in the global climate system.