This study provides evidence that the Great Pacific Garbage Patch (GPGP) is rapidly accumulating plastic. Using a model calibrated with data from multi-vessel and aircraft surveys, the researchers estimated that at least 79,000 tonnes of ocean plastic are floating within an area of 1.6 million km², four to sixteen times higher than previously reported. The difference is attributed to more robust methods for quantifying larger debris. Over three-quarters of the GPGP mass was carried by debris larger than 5 cm, with at least 46% being fishing nets. Microplastics accounted for 8% of the total mass but 94% of the estimated 1.8 trillion pieces. The results suggest that ocean plastic pollution within the GPGP is increasing exponentially and at a faster rate than in surrounding waters. Global annual plastic consumption has reached over 320 million tonnes, with more plastic produced in the last decade than ever before. A significant amount of this plastic is rapidly converted into waste, with the majority discarded into landfills or littered into natural environments, including the world's oceans. Fishing gear, particularly lost or discarded nets (ghostnets), is a major source of ocean plastic pollution. Around 60% of the plastic produced is less dense than seawater and can be transported by surface currents and winds, degraded into smaller pieces, or lose buoyancy and sink. A considerable accumulation zone for buoyant plastic was identified in the eastern part of the North Pacific Subtropical Gyre, commonly referred to as the GPGP. The study characterized and quantified buoyant ocean plastics within the GPGP. Between July and September 2015, a multi-vessel expedition collected surface trawl samples within and around the GPGP region. In October 2016, an aerial survey was conducted to obtain geo-referenced imagery that sampled greater sea surface area and improved estimations for debris larger than 0.5 m. The final dataset was used to calibrate a multi-source and multi-forcing ocean plastic transport model. The model was calibrated using monthly averages of predicted concentrations that reflected seasonal and inter-annual changes of the GPGP position. This study is the first attempt at introducing a time-coherent dynamic model of floating debris accumulation in the GPGP. The model predicted that the GPGP contains a total of 1.8 trillion plastic pieces weighing 79,000 tonnes, comprised of debris in four size classes: microplastics (0.05–0.5 cm), mesoplastics (0.5–5 cm), macroplastics (5–50 cm), and megaplastics (>50 cm). Over three-quarters of the GPGP plastic mass was contained in the upper size classes, with macroplastics and megaplastics contributing 25% and 53%, respectively. PlasticThis study provides evidence that the Great Pacific Garbage Patch (GPGP) is rapidly accumulating plastic. Using a model calibrated with data from multi-vessel and aircraft surveys, the researchers estimated that at least 79,000 tonnes of ocean plastic are floating within an area of 1.6 million km², four to sixteen times higher than previously reported. The difference is attributed to more robust methods for quantifying larger debris. Over three-quarters of the GPGP mass was carried by debris larger than 5 cm, with at least 46% being fishing nets. Microplastics accounted for 8% of the total mass but 94% of the estimated 1.8 trillion pieces. The results suggest that ocean plastic pollution within the GPGP is increasing exponentially and at a faster rate than in surrounding waters. Global annual plastic consumption has reached over 320 million tonnes, with more plastic produced in the last decade than ever before. A significant amount of this plastic is rapidly converted into waste, with the majority discarded into landfills or littered into natural environments, including the world's oceans. Fishing gear, particularly lost or discarded nets (ghostnets), is a major source of ocean plastic pollution. Around 60% of the plastic produced is less dense than seawater and can be transported by surface currents and winds, degraded into smaller pieces, or lose buoyancy and sink. A considerable accumulation zone for buoyant plastic was identified in the eastern part of the North Pacific Subtropical Gyre, commonly referred to as the GPGP. The study characterized and quantified buoyant ocean plastics within the GPGP. Between July and September 2015, a multi-vessel expedition collected surface trawl samples within and around the GPGP region. In October 2016, an aerial survey was conducted to obtain geo-referenced imagery that sampled greater sea surface area and improved estimations for debris larger than 0.5 m. The final dataset was used to calibrate a multi-source and multi-forcing ocean plastic transport model. The model was calibrated using monthly averages of predicted concentrations that reflected seasonal and inter-annual changes of the GPGP position. This study is the first attempt at introducing a time-coherent dynamic model of floating debris accumulation in the GPGP. The model predicted that the GPGP contains a total of 1.8 trillion plastic pieces weighing 79,000 tonnes, comprised of debris in four size classes: microplastics (0.05–0.5 cm), mesoplastics (0.5–5 cm), macroplastics (5–50 cm), and megaplastics (>50 cm). Over three-quarters of the GPGP plastic mass was contained in the upper size classes, with macroplastics and megaplastics contributing 25% and 53%, respectively. Plastic