Joint Oceanographic Institutions, United States

A prototype tool to continuously monitor temperature, pressure, and conductivity (TPC) changes during Ocean Drilling Program (ODP) coring was used successfully 107 times at Hydrate Ridge during Leg 204. TPC sensors are located on the face of the standard ODP advanced piston corer piston, and the data logging electronics and batteries are embedded within the piston. This tool operates autonomously and requires little shipboard attention. The objective is to measure the temperature and pressure changes that occur in gas-rich and gas hydrate-bearing cores during collection and ascent to the surface and to use these data to learn about the processes that occur inside a core during recovery. Gas exsolution and expansion during core recovery alter both the temperature and pressure conditions within the core barrel, and the amount of gas in the core affects where these changes occur. The core collection process dramatically affects pressure inside the core barrel, which reduces core temperature and changes gas saturation conditions. Families of temperature-time curves generated from TPC data show distinct cooling anomalies associated with core pullout and with movement of the core through the shallow water column and on the deck of the drillship. Here the performance of the TPC tool and the response of the tool at sites with significant quantities of sediment gas and gas hydrate near the seafloor are described.