From Raw Data to Insights: How to Calculate Heat Flow from Measurements

After successfully deploying the Giant Heat Flow Probe and collecting temperature data from the seabed, the next crucial step is data reduction and heat flow calculation. In this blog post, I’ll walk you through how we process the raw measurements and derive meaningful insights about Earth's internal heat. Get ready for some math!

Step 1: Data Collection and Initial Processing
From last time we learned that the probe records:

• The natural background temperature at various depths within the sediment.
• The response to a controlled heat pulse, which helps determine thermal conductivity.

Step 2: Temperature Equilibration and Gradient Determination
When the probe penetrates the seabed, friction generates excess heat. To ensure accurate readings, we allow time (typically ~10 minutes) for this excess heat to dissipate and for the sediment temperature to stabilize. Once equilibrium is reached (blue dashed window in Figure), we analyze the recorded temperature profile to determine the geothermal gradient--the rate at which temperature increases with depth.

Mathematically, the geothermal gradient is calculated as:
ⅆT/ⅆz=(T2-T1)/(z2-z1 )
Where T1 and T2 are temperatures at depths z1 and z2, respectively.

Step 3: Thermal Conductivity Measurement
To compute heat flow, we also need the thermal conductivity (k) of the sediment. This is obtained using the heat pulse method: a known amount of heat is introduced, and the temperature response is recorded. The rate at which the sediment absorbs and dissipates this heat allows us to calculate its thermal conductivity (red dashed window in Figure).

Step 4: Calculating Heat Flow
Once we have the geothermal gradient and thermal conductivity, we can determine the heat flow using Fourier’s Law:
q=-k ⅆT/ⅆz
This equation describes how heat moves through the sediment, with higher values indicating more heat escaping from the Earth's interior.

Looking Ahead
With our heat flow values in hand, the next step is correcting for external influences and later integrating them into broader geophysical models. Stay tuned as we analyze our dataset further and explore what these measurements reveal about the hidden thermal processes beneath the ocean floor!
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Dr. Florian Neumann
MARUM, University of Bremen