[Paper Review] Heat-flash travel just above a deep Mediterranean seafloor

van Haren, Hans|arXiv (Cornell University)|Jan 8, 2026

Oceanographic and Atmospheric Processes0 citations

TL;DR

The paper documents rare near-seafloor heat flashes traveling above a deep Mediterranean seafloor, likely linked to internal-wave instabilities, and compares them with signals from an ROV and other possible sources.

ABSTRACT

The deep sea is weakly stratified in density but shows considerable variations in turbulent motions in all three directions. When registered by moored high-resolution temperature 'T'-sensors, the motions cause variations of 0.01degrC or less and in time of minutes or less, which is much faster than hours or longer of internal waves. Occasionally, T-sensors close to the seafloor register minute-long flashes of 0.0005-0.001degrC warmer than the environment. When singular, such flashes may be artefacts. However, in a large mooring-array with 45 vertical lines at 9.5-m horizontal distances, near-seafloor heat flashes are seen to travel, most likely with internal-wave instabilities in overlying stratified waters. The instabilities seem to release the flashes from a geothermally heated seafloor of which turbulence convection is suppressed by warmer waters from above. The forms and turbulence intensity of these rare signals are compared with those induced by a Remotely Operated Vehicle working near the array. Other causes like unidentified marine mammal passing are hypothesized.

Motivation & Objective

• Investigate rapid, minute-scale temperature fluctuations near the deep seafloor.
• Characterize the occurrence, duration, and magnitude of near-seafloor heat flashes.
• Assess potential physical mechanisms causing these flashes, especially internal-wave instabilities.
• Compare observed signals with disturbances introduced by an ROV and explore other plausible sources.

Proposed method

• Use high-resolution moored temperature sensors to detect tiny temperature variations down to 0.01°C.
• Identify and analyze near-seafloor heat flashes lasting about a minute with amplitudes of 0.0005–0.001°C.
• Employ a large mooring array with 45 vertical lines at ~9.5 m horizontal spacing to track flashes.
• Interpret flashes as likely due to internal-wave instabilities releasing heat from a geothermally heated seafloor.
• Compare observed signals with disturbances from an adjacent Remotely Operated Vehicle (ROV) and hypothesize other causes (e.g., marine mammals).

Experimental results

Research questions

• RQ1 Do minute-long near-seafloor heat flashes occur above a deep Mediterranean seafloor?
• RQ2 Are these flashes consistent with internal-wave instabilities or other known perturbation sources?
• RQ3 How do the flashes compare to signals induced by an ROV near the sensor array?
• RQ4 What are the potential sources beyond internal-wave instabilities that could generate such flashes?

Key findings

• Near-seafloor sensors register rare, minute-long heat flashes of 0.0005–0.001°C above the environment.
• Flashes travel within the vertical mooring array, suggesting a propagating phenomenon likely linked to internal-wave instabilities.
• The instabilities seem to release warmth from a geothermally heated seafloor, with overlying warmer waters suppressing turbulence convection.
• Signals are compared to ROV-induced disturbances, and other sources such as unidentified marine mammals are hypothesized.