OpenMetBuoy-v2021: An Easy-to-Build, Affordable, Customizable, Open-Source Instrument for Oceanographic Measurements of Drift and Waves in Sea Ice and the Open Ocean

Abstract

There is a wide consensus within the polar science, meteorology, and oceanography communities that more in situ observations of the ocean, atmosphere, and sea ice are required to further improve operational forecasting model skills. Traditionally, the volume of such measurements has been limited by the high cost of commercially available instruments. An increasingly attractive solution to this cost issue is to use instruments produced in-house from open-source hardware, firmware, and postprocessing building blocks. In the present work, we release the next iteration of the open-source drifter and wave-monitoring instrument of Rabault et al. (see “An open source, versatile, affordable waves in ice instrument for scientific measurements in the Polar Regions”, Cold Regions Science and Technology, 2020), which follows these solution aspects. The new design is significantly less expensive (typically by a factor of 5 compared with our previous, already cost-effective instrument), much easier to build and assemble for people without specific microelectronics and programming competence, more easily extendable and customizable, and two orders of magnitude more power-efficient (to the point where solar panels are no longer needed even for long-term deployments). Improving performance and reducing noise levels and costs compared with our previous generation of instruments is possible in large part thanks to progress from the electronics component industry. As a result, we believe that this will allow scientists in geosciences to increase by an order of magnitude the amount of in situ data they can collect under a constant instrumentation budget. In the following, we offer (1) a detailed overview of our hardware and software solution, (2) in situ validation and benchmarking of our instrument, (3) a fully open-source release of both hardware and software blueprints. We hope that this work, and the associated open-source release, will be a milestone that will allow our scientific fields to transition towards open-source, community-driven instrumentation. We believe that this could have a considerable impact on many fields by making in situ instrumentation at least an order of magnitude less expensive and more customizable than it has been for the last 50 years, marking the start of a new paradigm in oceanography and polar science, where instrumentation is an inexpensive commodity and in situ data are easier and less expensive to collect.

A dataset of direct observations of sea ice drift and waves in ice

“…In the course of the data collection, several instrument models have been used. These are, the instrument "v2018" 46 , the instrument "v2021" 47,48 , the Sofar Spotter buoy 49 , commercial Global Positioning System (GPS) drifters with Iridium communication ability, and the Ice Wave Rider (IWR) 50 . All instruments use GPS to measure geographical location.…”

“…The instruments v2018, v2021, and IWR, use Inertial Measurement Units (IMUs) to measure the wave motion. In the following paragraphs, we outline the main lines of the data acquisition and the wave processing algorithms, though the reader curious of the exact, in-depth technical details regarding the open source instruments, is referred to the technical papers 46,47,50 that go deeper into the exact implementation, or to the code implementing the data processing (see the previous Github links).…”

“…• In the case of the v2021 47 , the temperature-compensated 9-degree-of-freedom (9dof) sensor measures the accelerations, angular rates, and the local magnetic field, each over 3 axis (the X, Y, and Z axis of the 9dof sensor, in its own frame of reference attached to the microchip itself). These raw measurements are performed at 800Hz.…”

“…• In the case of the instrument v2021 47 , a slightly simpler methodology is used. The Power Spectral Density (PSD) for the vertical wave acceleration PSD accD is directly calculated from the vertical wave acceleration data at 10Hz, by applying the Welch method on 20.48 minutes of data (so that the exact number of samples is a multiple of 2 11 , which makes the calculation of the FFTs and the splitting into segments simpler and faster).…”

“…Results that come from in-situ processing of IMU or GPS data, such as the wave spectra and statistics reported by the Sofar Spotter and the instruments v2018 and v2021, have been previously validated in details, and the reports and validation details are available in the literature: the Sofar Spotter is a commercial instrument that was validated before being released for sale 49 , the v2018 has been validated and used in scientific papers multiple times 36,46,70 , and the v2021 has been recently validated against both commercial buoys and satellite data 47 . Validation campaigns for both the v2018 and the v2021 indicated agreement to either within 5%, or within one standard deviation, of commercial instrument or other measurement methodology.…”