When Tides Run Dry: Exploring an Overlooked Coastal Disturbance and Its Climate Connections

Area of Science:

• Marine biology
• Oceanography
• Climate science

Background:

• Weakening polar temperature gradients drive persistent weather, increasing extreme events.
• Marine heat waves are well-studied, but negative sea level anomalies (Dry Tides) are understudied.
• Dry Tides cause physiological stress and alter coastal community structure.

Purpose of the Study:

• Define and quantify extreme negative sea level anomalies (Dry Tides).
• Assess global frequency, intensity, and duration of Dry Tides.
• Investigate trends and drivers of Dry Tides.

Main Methods:

• Defined Dry Tides as water level depressions below the 10th percentile for over 5 days.
• Analyzed global tidal gauge records from 25 locations.
• Quantified event duration, amplitude, and frequency.

Main Results:

• Dry Tides occur globally, most frequent in microtidal/semi-enclosed systems.
• Events last 1-2 weeks, with extremes up to 97 days and 37% tidal range depression.
• No consistent increase in Dry Tide frequency or intensity observed over 30 years.

Conclusions:

• Dry Tides are influenced by interacting physical drivers, not a single cause.
• Ecological impacts require further study, integrating physical and biological data.
• Tools for Dry Tide identification are provided for local assessment.