Abstract: As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.

Abstract: Beside the physical impacts of climate change, society's perceptions of climate change and its reactions at different stages of decision-making levels have become critical issues. This study presents the perspective of tourists who have previously visited Florida, in a hypothetical scenario of changed climatic conditions. It is proposed that existing social representations about climate change, and therefore individuals' attitudes, views, and beliefs about this phenomenon, need to be taken into account when examining tourists' stated responses to climate change and subsequent potential shifts in tourism demand. The existence of a relationship between tourists' visitation intentions toward a destination impacted by climate change and the social representations they hold with respect to climate change itself offers an alternative way to look at tourists' stated responses. This study concludes that predicting shifts in tourism demand based on tourist visitation intentions requires caution when dealing with climate change.

Abstract: Inter-annual to decadal sea level variations from tide gauge records in the coastal zones of the Norwegian and Siberian Seas are examined for the period 1950-2010 using a combination of hydrographic observations, wind data, and theory. We identify two large areas of highly coherent sea level variability: one that includes the Norwegian, Barents, and Kara Seas, and another one that includes the Laptev, East Siberian, and Chukchi Seas. We provide evidence of a new contribution to the sea level variability along the Norwegian coast associated with the poleward propagation of sea level fluctuations along the eastern boundary of the North Atlantic. When this propagating signal is combined with the local wind we are able to explain over 70% of the variance along the Norwegian coast. The steric component explains ~61% of the sea level (corrected for the inverse barometer) variability along the Norwegian coast. The high coherency between the sea level along the Norwegian coast and that in the Barents and Kara Seas suggests that part of the Norwegian signal propagates further north into these regions. We introduce an atmospheric vorcity index that explains much of the sea level variability in the Laptev, East Siberian, and Chukchi Seas with correlations ranging from 0.73 to 0.81. In the East Siberian Sea, we identify a sea level increase of ~22 cm between 2000 and 2003, which is partly explained by the vorticity index, and a decline of ~15 cm after 2003, which we relate to the strengthening of the Beaufort Gyre.

Abstract: Climate change is a significant global risk that is predicted to be particularly devastating to coastal communities. Climate change adaptation and mitigation have been hindered by many factors, including psychological barriers, ineffective outreach and communication, and knowledge gaps. This qualitative study compares an expert model of climate change risks to county administrators' mental models of climate change and related coastal environmental hazards in Crystal River, Florida, USA. There were 24 common nodes in the expert and the combined non-expert models, mainly related to hurricanes, property damage, and economic concerns. Seven nodes mentioned by non-experts fit within, but were not a part of, the expert model, primarily related to ecological concerns about water quality. The findings suggest that effective climate outreach and communication could focus on compatible parts of the models and incorporate local concerns to find less controversial ways to discuss climate-related hazards.

Abstract: Shifts in microbial community function and structure can be indicators of environmental stress and ecosystem change in wetland soils. This study evaluated the effects of increased salinity, increased inundation, and their combination, on soil microbial function (enzyme activity) and structure (phospholipid fatty acid (PLFA) signatures and terminal restriction fragment length polymorphisms (T-RFLP) profiles) in a brackish mangrove peat soil using tidal mesocosms (Everglades, Florida, USA). Increased tidal inundation resulted in reduced soil enzyme activity, especially alkaline phosphatase, an increase in the abundance and diversity of prokaryotes, and a decline in number of eukaryotes. The community composition of less abundant bacteria (T-RFLPs comprising 0.3-1 % of total fluorescence) also shifted as a result of increased inundation under ambient salinity. Several key biogeochemical indicators (oxidation-reduction potential, CO2 flux, porewater NH4 (+), and dissolved organic carbon) correlated with measured microbial parameters and differed with inundation level. This study indicates microbial function and composition in brackish soil is more strongly impacted by increased inundation than increased salinity. The observed divergence of microbial indicators within a short time span (10-weeks) demonstrates their usefulness as an early warning signal for shifts in coastal wetland ecosystems due to sea level rise stressors.

Abstract: The IPCC 2013 Wetlands Supplement provided new guidance for countries on inclusion of wetlands in their National GHG Inventories. The United States has responded by including managed coastal wetlands for the first time in its 2017 GHG Inventory report along with an updated time series in the most recent 2018 submission and plans to update the time series on an annual basis as part of its yearly submission to the United Nations Framework Convention on Climate Change (UNFCCC). The United States followed IPCC Good Practice Guidance when reporting sources and sinks associated with managed coastal wetlands. Here we show that intact vegetated coastal wetlands are a net sink for GHGs. Despite robust regulation that has protected substantial stocks of carbon, the United States continues to lose coastal wetlands to development and the largest loss of wetlands to open water occurs around the Mississippi Delta due mostly to upstream changes in hydrology and sediment delivery, and oil and gas extraction. These processes create GHG emissions. By applying comprehensive Inventory reporting, scientists in the United States have identified opportunities for reducing GHG emissions through restoration of coastal wetlands that also provide many important societal co-benefits.

Abstract: Saltwater intrusion is a major hazard to coastal communities as it causes degradation of fresh water resources. The impact of rising sea level on the saltwater intrusion into coastal aquifers has been studied for decades, but how human activities affect the extent of saltwater intrusion is poorly understood. Human activities are known to influence groundwater availability indirectly by affecting precipitation patterns and directly by extracting groundwater and reducing recharge. In this paper the authors investigated the integrated impacts of human activities and rising sea level on aquifer recharge in Quintana Roo, Mexico, by incorporating anthropogenic impacts on groundwater recharge into an analytical saltwater intrusion model. The impact of human activities on groundwater extraction was firstly calculated; then, the resulting groundwater recharge was used in a Ghyben�Herzberg analytical model to determine the inland distance of saltwater intrusion. The analytical model tested six scenarios stemming from different combinations of human development patterns, hydrological settings, hydraulic conditions and rising sea level to obtain the range of possible inland movement of saltwater intrusion. Our results indicate that the groundwater recharge will decrease to 32.6 mm year−1 if human activities increase by 50 % more. With 1-m sea level rise, inland saltwater intrusion distance is estimated to be up to 150 and 1 km under head-controlled and flux-controlled scenarios, respectively. A sensitivity analysis of the model reveals that the large hydraulic conductivity of the Quintana Roo aquifer (0.26�68.8 m s−1) is the most important factor in determining saltwater intrusion distance. Therefore, in this aquifer, the response to human activities is greatly exceeded by natural hydrogeological conditions.