In Situ Optical Sensor for Measuring Particulate Inorganic Carbon in Seawater

IB-1595

E.O. Lawrence Berkeley National Laboratory

APPLICATION OF TECHNOLOGY:

• Advance the current state of knowledge regarding the functioning of the biological pump and its consequences for global carbon cycling
• Long-term deployments on conventional, autonomous, oceanographic platforms
• Next-generation oceanographic platforms.
• Auxiliary sensor on CTD profilers
• Basic earth sciences research
• Monitoring and regulatory efforts

Light transmitted through parallel (left) and crossed (right) polarizers by birefringent CaCO3 and two non-birefringent minerals (halite and SiO2). Only the birefringent calcite (CaCO3) allows light to pass through crossed polarizers.

ADVANTAGES:

• Enable data to be collected on more extensive spatial scales than currently possible;
• Allow work to be conducted in harsh environments and remote areas otherwise impractical or impossible to access
• Improve computer-based simulations and forecasted responses to different greenhouse gas emission scenarios

ABSTRACT:

The transport of biogenic carbon from the surface to deep ocean (commonly referred to as the "biological pump") plays a critical role in regulating the level of CO₂ in the Earth's atmosphere. Understanding of the biological pump is severely limited because conventional, ship-based sampling methods cannot adequately capture the spatial and temporal variability of biomass and carbon species in the ocean. To advance the current state of knowledge regarding the functioning of the biological pump and its consequences for global carbon cycling, James Bishop and Christopher Guay of Berkeley Lab have designed a new optical sensor for making in situ measurements of particulate inorganic carbon (PIC) in seawater. PIC in the marine environment consists of biogenic particles of CaCO₃. Berkeley Lab's new sensor is based on a distinguishing mineralogical characteristic of CaCO₃ — its extreme birefringence. When viewed under a microscope in cross-polarized light, CaCO₃ crystals appear to light up, and this property can be used for making in situ determinations of PIC in the oceans. The instrument will ultimately be designed to have spatial dimensions, power requirements, and data storage/telemetry capacity appropriate for long-term deployments on conventional, autonomous, oceanographic platforms, as well as on next-generation platforms. Berkeley Lab's new, in situ, optical PIC sensor will be useful as an auxiliary sensor on CTD profilers; the sensor will enable data to be collected on more extensive spatial scales than currently possible; and it will allow work to be conducted in harsh environments and remote areas otherwise impractical or impossible to access. Successful development of this technology will represent a major advance in marine carbon system monitoring and lead to a greater understanding of the biological pump and its relation to global climate change, thus improving computer-based simulations and forecasted responses to different greenhouse gas emission scenarios. This important, new technology should therefore find applications in basic earth sciences research as well as monitoring and regulatory efforts.

STATUS: U.S. Patent #7,030,981. Available for licensing

REFERENCE NUMBER: IB-1595

FOR ADDITIONAL INFORMATION:

• Publication: Christopher Guay, James Bishop, "A Rapid Briefringence Method for Mesasuring Suspended CaCO₃ Concentrations in Seawater," Pergamon, Deep-Sea Research part I, 49 (2002), 197-210.