Abstract
Ocean warming ‘hotspots’ are regions characterized by above‐average temperature increases over recent years, for which there are significant consequences for both living marine resources and the societies that depend on them. As such, they represent early warning systems for understanding the impacts of marine climate change, and test‐beds for developing adaptation options for coping with those impacts. Here, we examine five hotspots off the coasts of eastern Australia, South Africa, Madagascar, India and Brazil. These particular hotspots have underpinned a large international partnership that is working towards improving community adaptation by characterizing, assessing and projecting the likely future of coastal‐marine food resources through the provision and sharing of knowledge. To inform this effort, we employ a high‐resolution global ocean model forced by Representative Concentration Pathway 8.5 and simulated to year 2099. In addition to the sea surface temperature, we analyse projected stratification, nutrient supply, primary production, anthropogenic CO 2‐driven ocean acidification, deoxygenation and ocean circulation. Our simulation finds that the temperature‐defined hotspots studied here will continue to experience warming but, with the exception of eastern Australia, may not remain the fastest warming ocean areas over the next century as the strongest warming is projected to occur in the subpolar and polar areas of the Northern Hemisphere. Additionally, we find that recent rapid change in SST is not necessarily an indicator that these areas are also hotspots of the other climatic stressors examined. However, a consistent facet of the hotspots studied here is that they are all strongly influenced by ocean circulation, which has already shown changes in the recent past and is projected to undergo further strong change into the future. In addition to the fast warming, change in local ocean circulation represents a distinct feature of present and future climate change impacting marine ecosystems in these areas.
Highlights
Footprints of climate change have been reported for most major marine ecosystems around the world (e.g. Hoegh-Guldberg & Bruno, 2010; Hobday & Lough, 2011; Wassmann et al, 2011; Okey et al, 2014)
The concept of marine warming hotspots suggested by HP14 on the basis of historical sea surface temperature (SST) data builds on a considerable literature defining hotspots for biodiversity (e.g. Myers, 2003)
In our assessment of climatic stressors on ocean ecosystems, we suggest that the main question that should be asked is when a stressor begins to fall outside of either the range of natural or a baseline variability, and if such an occurrence is part of a consistent trend
Summary
Footprints of climate change have been reported for most major marine ecosystems around the world (e.g. Hoegh-Guldberg & Bruno, 2010; Hobday & Lough, 2011; Wassmann et al, 2011; Okey et al, 2014). Coastal-marine food resources will alter as a result of species-specific direct responses to drivers of climate change, such as distribution and abundance of species changing in response to temperature, as already reported from south-east Australia (Frusher et al, 2014), or ocean acidification in the Arctic Mathis et al, 2015) Such impacts to living marine resources will require individuals, communities, industries and governments to understand and adapt to the changing climate Adaptation options within the context of climate change must build on a solid understanding of the physical, biological and human aspects of the given systems, and a recognition that marine systems and human societies are really parts of a unified marine socio-ecological system (Perry et al, 2010)
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