Global ocean temperatures are rising, yet the impacts of such changes on harmful algal blooms (HABs) are not fully understood. Here we used high-resolution sea-surface temperature records (1982 to 2016) and temperature-dependent growth rates of two algae that produce potent biotoxins, Alexandrium fundyense and Dinophysis acuminata, to evaluate recent changes in these HABs. For both species, potential mean annual growth rates and duration of bloom seasons significantly increased within many coastal Atlantic regions between 40°N and 60°N, where incidents of these HABs have emerged and expanded in recent decades. Widespread trends were less evident across the North Pacific, although regions were identified across the Salish Sea and along the Alaskan coastline where blooms have recently emerged, and there have been significant increases in the potential growth rates and duration of these HAB events. We conclude that increasing ocean temperature is an important factor facilitating the intensification of these, and likely other, HABs and thus contributes to an expanding human health threat.Alexandrium | Dinophysis | climate change | sea-surface temperature | bloom duration H armful algal blooms (HABs) negatively affect aquatic ecosystems, fisheries, tourism, and human health. HABs such as Alexandrium fundyense and Dinophysis acuminata are particularly concerning, as they produce saxitoxin and okadaic acid, respectively, toxins that can cause the human health syndromes paralytic and diarrhetic shellfish poisoning (PSP and DSP, respectively). The global range, regional intensity, and frequency of HABs have increased in recent decades (1, 2). This phenomenon is, in part, related to increasing awareness and improved monitoring of HABs (2) and, in some cases, the intensification of anthropogenic nutrient loading in coastal zones (3). Although there have been multiple predictions regarding the response of HABs to future climate change (2, 4), the ability to conclusively relate changes in HAB phenology and distribution to rising ocean temperatures has been a challenge.Globally, the geographic ranges of phytoplankton are frequently controlled by sea-surface temperatures [SSTs (2, 5)], and the realized niches of HABs are often defined by a narrow range of temperatures (2, 5-8). As global oceans warm (9, 10) and the distribution of ocean temperatures changes (11,12), it is expected that the distribution and range of phytoplankton and HABs will also shift (2, 4). Observations and modeling studies have shown that climate change-driven warming of ocean water is unevenly distributed (12), particularly along coastlines (11, 13). Consequently, temperature-driven changes in HAB distributions are likely to vary along coastlines and among ocean basins. Presently, the extent to which changes in HAB occurrence and intensity are related to changing ocean temperatures is unresolved.To assess the relationship between HABs and global temperature change, some recent studies have used physical and biogeochemical output from global circulation ...

Aeolian dust is a key aspect of the climate system. Dust can modify the Earth's energy budget, provide long-range transport of nutrients, and influence land surface processes via erosion. Consequently, effective modeling of the climate system, particularly at regional scales, requires a reasonably accurate representation of dust emission, transport, and deposition. Here we evaluate African dust in 23 state-of-the-art global climate models used in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. We find that all models fail to reproduce basic aspects of dust emission and transport over the second half of the twentieth century. The models systematically underestimate dust emission, transport, and optical depth, and year-to-year changes in these properties bear little resemblance to observations. These findings cast doubt on the ability of these models to simulate the regional climate and the response of African dust to future climate change.

Over the last few decades, rising greenhouse gas emissions have promoted poleward expansion of the large-scale atmospheric Hadley circulation that dominates the Tropics, thereby affecting behavior of the Intertropical Convergence Zone (ITCZ) and North Atlantic Oscillation (NAO). Expression of these changes in tropical marine ecosystems is poorly understood because of sparse observational datasets. We link contemporary ecological changes in the southern Caribbean Sea to global climate change indices. Monthly observations from the CARIACO Ocean Time-Series between 1996 and 2010 document significant decadal scale trends, including a net sea surface temperature (SST) rise of ∼1.0 ± 0.14°C (±SE), intensified stratification, reduced delivery of upwelled nutrients to surface waters, and diminished phytoplankton bloom intensities evident as overall declines in chlorophyll a concentrations (ΔChla = −2.8 ± 0.5%·y −1 ) and net primary production (ΔNPP = −1.5 ± 0.3%·y −1 ). Additionally, phytoplankton taxon dominance shifted from diatoms, dinoflagellates, and coccolithophorids to smaller taxa after 2004, whereas mesozooplankton biomass increased and commercial landings of planktivorous sardines collapsed. Collectively, our results reveal an ecological state change in this planktonic system. The weakening trend in Trade Winds (−1.9 ± 0.3%·y −1 ) and dependent local variables are largely explained by trends in two climatic indices, namely the northward migration of the Azores High pressure center (descending branch of Hadley cell) by 1.12 ± 0.42°N latitude and the northeasterly progression of the ITCZ Atlantic centroid (ascending branch of Hadley cell), the March position of which shifted by about 800 km between 1996 and 2009. ecosystem state change | oceanography | plankton productivity P hytoplankton support over 95% of marine food webs and are responsible for about half of the Earth's conversion of CO 2 to biomass through net primary production (NPP) (1). Long-term declines in phytoplankton biomass and production in over 70% of the global ocean have been inferred recently from satellite imagery and century-long shipboard records of water clarity (2, 3). These reports of large-scale changes are at odds with trends directly observed at specific locations within the same ocean domains.

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