Measuring Earth’s Hidden Heat: Exploring the Giant Heat Flow Probe on NBP-25-01

Hi everyone, it's me again—Florian, the Heat-Flow guy on Cruise NBP-25-01!

Before diving into the details of how we measure heat flow, I have some exciting news—we got our first measurement! Even better, we got 43!

In this episode, we’ll take a closer look at the Giant Heat Flow Probe (pictures included).

On this cruise, we’re using a 6-meter-long "Violin Bow Style" Heat Flow Probe, a tool designed to measure temperature in the seafloor to ultimately calculate how much heat is escaping from inside the Earth. The probe consists of a long metal rod, called the strength member, with a sensor string (shaped like a violin bow) attached to it. This string houses 22 thermistors (high-precision thermometers) that record temperature within the sediment. At the top of the probe, the head unit contains the electronics that record all the data and adds the necessary weight to help the probe penetrate the seafloor.

The probe is lowered from the ship and driven into the seabed by its own weight—an impressive one metric ton. Once in place, it waits about 10 minutes for any frictional heat from penetration to dissipate. Then, a heat pulse is fired, and the thermistors (15 active ones in our case) measure how quickly the surrounding sediment absorbs and releases this heat. This data allows us to calculate how much heat is flowing from inside the Earth.
After the measurement, the probe is retrieved, and we analyze the data to gain insights into the thermal environment beneath the ocean floor.

Next time, we’ll explore how we calculate heat flow from these measurements—stay tuned!

Dr. Florian Neumann
MARUM, University of Bremen