Changing climate threatens the health and well-being of people in the Northeast through more extreme weather, warmer temperatures, degradation of air and water quality, and sea level rise. These environmental changes are expected to lead to health-related impacts and costs, including additional deaths, emergency room visits and hospitalizations, and a lower quality of life. Health impacts are expected to vary by location, age, current health, and other characteristics of individuals and communities.

The seasonality of the Northeast is central to the region’s sense of place and is an important driver of rural economies. Less distinct seasons with milder winter and earlier spring conditions are already altering ecosystems and environments in ways that adversely impact tourism, farming, and forestry. The region’s rural industries and livelihoods are at risk from further changes to forests, wildlife, snowpack, and streamflow.

Changing climate threatens the health and well-being of people in the Northeast through more extreme weather, warmer temperatures, degradation of air and water quality, and sea level rise. These environmental changes are expected to lead to health-related impacts and costs, including additional deaths, emergency room visits and hospitalizations, and a lower quality of life. Health impacts are expected to vary by location, age, current health, and other characteristics of individuals and communities.

The seasonality of the Northeast is central to the region’s sense of place and is an important driver of rural economies. Less distinct seasons with milder winter and earlier spring conditions are already altering ecosystems and environments in ways that adversely impact tourism, farming, and forestry. The region’s rural industries and livelihoods are at risk from further changes to forests, wildlife, snowpack, and streamflow.

Communities, towns, cities, counties, states, and tribes across the Northeast are engaged in efforts to build resilience to environmental challenges and adapt to a changing climate. Developing and implementing climate adaptation strategies in daily practice often occur in collaboration with state and federal agencies (e.g., New Jersey Climate Adaptation Alliance 2017, New York Climate Clearinghouse 2017, Rhode Island STORMTOOLS 2017, EPA 2017, CDC 2015 30 , 31 , 32 , 33 , 34 ). Advances in rural towns, cities, and suburban areas include low-cost adjustments of existing building codes and standards. In coastal areas, partnerships among local communities and federal and state agencies leverage federal adaptation tools and decision support frameworks (for example, NOAA’s Digital Coast, USGS’s Coastal Change Hazards Portal, and New Jersey’s Getting to Resilience). Increasingly, cities and towns across the Northeast are developing or implementing plans for adaptation and resilience in the face of changing climate (e.g., EPA 2017 33 ). The approaches are designed to maintain and enhance the everyday lives of residents and promote economic development. In some cities, adaptation planning has been used to respond to present and future challenges in the built environment. Regional efforts have recommended changes in design standards when building, replacing, or retrofitting infrastructure to account for a changing climate.

Increases in annual average temperatures across the Northeast range from less than 1°F (0.6°C) in West Virginia to about 3°F (1.7°C) or more in New England since 1901. 18 , 19 Although the relative risk of death on very hot days is lower today than it was a few decades ago, heat-related illness and death remain significant public health problems in the Northeast. 20 , 21 , 22 , 23 For example, a study in New York City estimated that in 2013 there were 133 excess deaths due to extreme heat. 24 These projected increases in temperature are expected to lead to substantially more premature deaths, hospital admissions, and emergency department visits across the Northeast. 23 , 25 , 26 , 27 , 28 , 29 For example, in the Northeast we can expect approximately 650 additional premature deaths per year from extreme heat by the year 2050 under either a lower (RCP4.5) or higher (RCP8.5) scenario and from 960 (under RCP4.5) to 2,300 (under RCP8.5) more premature deaths per year by 2090. 29

Northeastern cities, with their abundance of concrete and asphalt and relative lack of vegetation, tend to have higher temperatures than surrounding regions due to the urban heat island effect. During extreme heat events, nighttime temperatures in the region’s big cities are generally several degrees higher than surrounding regions, leading to higher risk of heat-related death. Urban areas are at risk for large numbers of evacuated and displaced populations and damaged infrastructure due to both extreme precipitation events and recurrent flooding, potentially requiring significant emergency response efforts and consideration of a long-term commitment to rebuilding and adaptation, and/or support for relocation where needed. Much of the infrastructure in the Northeast, including drainage and sewer systems, flood and storm protection assets, transportation systems, and power supply, is nearing the end of its planned life expectancy. Climate-related disruptions will only exacerbate existing issues with aging infrastructure. Sea level rise has amplified storm impacts in the Northeast (Key Message 2), contributing to higher surges that extend farther inland, as demonstrated in New York City in the aftermath of Superstorm Sandy in 2012. 14 , 15 , 16 Service and resource supply infrastructure in the Northeast is at increasing risk of disruption, resulting in lower quality of life, economic declines, and increased social inequality. 17 Loss of public services affects the capacity of communities to function as administrative and economic centers and triggers disruptions of interconnected supply chains ( Ch. 16: International, Key Message 1 ).

Ocean and coastal ecosystems are being affected by large changes in a variety of climate-related environmental conditions. These ecosystems support fishing and aquaculture, 5 tourism and recreation, and coastal communities. 6 Observed and projected increases in temperature, acidification, storm frequency and intensity, and sea levels are of particular concern for coastal and ocean ecosystems, as well as local communities and their interconnected social and economic systems. Increasing temperatures and changing seasonality on the Northeast Continental Shelf have affected marine organisms and the ecosystem in various ways. The warming trend experienced in the Northeast Continental Shelf has been associated with many fish and invertebrate species moving northward and to greater depths. 7 , 8 , 9 , 10 , 11 Because of the diversity of the Northeast’s coastal landscape, the impacts from storms and sea level rise will vary at different locations along the coast. 12 , 13

The distinct seasonality of the Northeast’s climate supports a diverse natural landscape adapted to the extremes of cold, snowy winters and warm to hot, humid summers. This natural landscape provides the economic and cultural foundation for many rural communities, which are largely supported by a diverse range of agricultural, tourism, and natural resource-dependent industries (see Ch. 10: Ag & Rural, Key Message 4 ). 1 The recent dominant trend in precipitation throughout the Northeast has been towards increases in rainfall intensity, 2 with increases in intensity exceeding those in other regions of the contiguous United States. Further increases in rainfall intensity are expected, 3 with increases in total precipitation expected during the winter and spring but with little change in the summer. 4 Monthly precipitation in the Northeast is projected to be about 1 inch greater for December through April by end of century (2070–2100) under the higher scenario (RCP8.5). 4

Maintaining functioning, sustainable communities in the face of climate change requires effective adaptation strategies that anticipate and buffer impacts, while also enabling communities to capitalize upon new opportunities. Many northeastern cities already have or are rapidly developing short-term and long-term plans to mitigate climate effects and to plan for efficient investments in sustainable development and long-term adaptation strategies. Although timely adaptation to climate-related impacts would help reduce threats to people’s health, safety, economic well-being, and ways of life, changes to those societal elements will not be avoided completely.

The changing climate of the Northeast threatens the health and well-being of residents through environmental changes that lead to health-related impacts and costs, including additional deaths, emergency room visits and hospitalizations, higher risk of infectious diseases, lower quality of life, and increased costs associated with healthcare utilization. Health impacts of climate change vary across people and communities of the Northeast and depend on social, socioeconomic, demographic, and societal factors; community adaptation efforts; and underlying individual vulnerability (see Key Message 5) (see also Ch. 28: Adaptation ).

Residents in urban areas face multiple climate hazards, including temperature extremes, episodes of poor air quality, recurrent waterfront and coastal flooding, and intense precipitation events that can lead to increased flooding on urban streams. These physical changes may lead to large numbers of evacuated and displaced populations and damaged infrastructure; sustaining communities may require significant investment and planning to provide emergency response efforts, a long-term commitment to rebuilding and adaptation, and support for relocation. Underrepresented communities, such as the poor, elderly, language-isolated, and recent immigrants, are more vulnerable due to their limited ability to prepare for and cope with extreme weather and climate events. 59 Service infrastructure in the Northeast is at increasing risk of disruption, resulting in lower quality of life, economic declines, and enhanced social inequality. 17 Interdependencies across critical infrastructure sectors such as water, energy, transportation, and telecommunication (and related climate security issues) can lead to cascading failures during extreme weather and climate-related disruptions ( Ch. 17: Complex Systems ). 17 , 59 , 60 The region’s high density of built environment sites and facilities, large number of historic structures, and older housing and infrastructure compared to other regions suggest that urban centers in the Northeast are particularly vulnerable to climate shifts and extreme weather events. For example, because much of the historical development of industry and commerce in New England occurred along rivers, canals, coasts, and other bodies of water, these areas often have a higher density of contaminated sites, waste management facilities, and petroleum storage facilities that are potentially vulnerable to flooding. As a result, increases in flood frequency or severity could increase the spread of contaminants into soils and waterways, resulting in increased risks to the health of nearby ecosystems, animals, and people—a set of phenomena well documented following Superstorm Sandy. 61 , 62 , 63

In rural areas, community identity is often built around the prominence of small, multigenerational, owner-operated businesses and the natural resources of the local area. Climate variability can affect human migration patterns 56 and may change flows into or out of the Northeast as well as between rural and urban locations. Published research in this area, however, is limited. The Northeast has long been losing residents to other regions of the country. 57 Droughts and flooding can adversely affect ecosystem function, farm economic viability, and land use. Although future projections of major floods remain ambiguous, more intense precipitation events ( Ch. 2: Climate, KM 6 ) 58 have increased the risk of some types of inland floods, particularly in valleys, where people, infrastructure, and agriculture tend to be concentrated. With little redundancy in their infrastructure and, therefore, limited economic resilience, many rural communities have limited ability to cope with climate-related changes.

The Northeast is quite varied geographically, with a wide spectrum of communities including densely populated cities and metropolitan regions and relatively remote hamlets and villages (Figure 18.1). Rural and urban areas have distinct vulnerabilities, impacts, and adaptation responses to climate change. 51 , 52 The urbanized parts of the Northeast are dependent on the neighboring rural areas’ natural and recreational services, while the rural communities are dependent on the economic vitality and wealth-generating capacity of the region’s major cities. Rural and urban communities together are under increasing threat of climate change and the resulting impacts, and adaptation strategies reveal their interdependence and opportunities for successful climate resilience. 51 Rural–urban linkages 53 , 54 , 55 in the region could also be altered by climate change impacts.

The region’s oceans and coasts support a rich maritime heritage and provide an iconic landscape, as well as economic and ecological services. Highly productive marshes, 37 , 38 fisheries, 39 , 40 ecosystems, 41 , 42 and coastal infrastructure 43 , 44 are sensitive to changing environmental conditions, including shifts in temperature, ocean acidification, sea level, storm surge, flooding, and erosion. Many of these changes are already affecting coastal and marine ecosystems, posing increasing risks to people, traditions, infrastructure, and economies (e.g., Colburn et al. 2016 45 ). These risks are exacerbated by increasing demands on these ecosystems to support human use and development. The Northeast has experienced some of the highest rates of sea level rise 46 and ocean warming 39 in the United States, and these exceptional increases relative to other regions are projected to continue through the end of the century. 47 , 48 , 49 , 50

The Northeast region is characterized by four distinct seasons and a diverse landscape that is central to the region’s cultural identity, quality of life, and economic success. It is both the most heavily forested and most densely populated region in the country. Residents have ready access to beaches, forests, and other natural areas and use them heavily for recreation. Colorful autumn foliage, winter recreation, and summer vacations in the mountains or at the beach are all important parts of the Northeast’s cultural identity, and this tourism contributes billions of dollars to the regional economy. The seasonal climate, natural systems, and accessibility of certain types of recreation are threatened by declining snow and ice, rising sea levels, and rising temperatures. By 2035, and under both lower and higher scenarios (RCP4.5 and RCP8.5), the Northeast is projected to be more than 3.6°F (2°C) warmer on average than during the preindustrial era. This would be the largest increase in the contiguous United States and would occur as much as two decades before global average temperatures reach a similar milestone. 36

Species that are particularly vulnerable to temperature and flow changes include stream invertebrates, freshwater mussels, amphibians, and coldwater fish. 66 , 131 , 143 For example, a recent study of the habitat suitable for dragonflies and damselflies (species that are a good indicator of ecosystem health along rivers) in the Northeast projected, under both the lower and higher scenarios (RCP4.5 and RCP8.5), habitat declines of 45%–99% by 2080, depending on the species. 144 Other particularly vulnerable groups include species with water-dependent habitats, such as salamanders and coldwater fish. 66 , 145 Increasing temperatures within freshwater streams threaten coldwater fisheries across northern New England and south through the Appalachian Mountains. A decrease in recreational fishing revenue is expected by end of this century under a higher scenario (RCP8.5) with the loss of coldwater habitat. 29 , 131 , 146

The projected changes in precipitation intensity and temperature seasonality would also affect streams and the biological communities that live in them. Freshwater aquatic ecosystems are vulnerable to changes in streamflow, higher temperatures, and reduced water quality. 131 Such ecosystems are especially vulnerable to increases in high flows, decreases in low flows, and the timing of snowmelt. 113 , 132 , 133 The impact of heavy precipitation on streamflows partly depends upon watershed conditions such as prior soil moisture and snowpack conditions, which vary throughout the year. 134 , 135 , 136 , 137 Although the annual minimum streamflows have increased during the last century, 138 , 139 , 140 late-summer warming 4 , 141 could lead to decreases in the minimum streamflows in the late summer and early fall by mid-century. 142

Studies suggest that Northeast agriculture, with nearly $21 billion in annual commodity sales, 122 will benefit from the changing climate over the next half-century 35 , 123 due to greater productivity over a longer growing season (Figure 18.3) (see also Ch. 10: Ag & Rural ). However, excess moisture is already a leading cause of crop loss in the Northeast. 35 Recent and projected increases in precipitation amount, intensity, and persistence 124 , 125 indicate increasing impacts on agricultural operations. Increased precipitation can result in soil compaction, 126 delays in planting, and reductions in the number of days when fields are workable. 127 If the trend in the frequency of heavy rainfall prior to the last frost continues, overly wet fields could potentially prevent Northeast farmers from taking full advantage of an earlier spring. 35 Increased soil erosion and agricultural runoff—including manure, fertilizer, and pesticides 128 , 129 —are linked to excess nutrient loading of water bodies as well as possible food safety or public health issues from food and waterborne infections. 130 Warmer winters are likely to increase livestock productivity in the Northeast 129 but are expected to also increase pressure from weeds and pests, 35 demand for pesticides, 128 and the risk of human health effects from increased chemical exposures. 130

The recent dominant trend in precipitation throughout the Northeast has been towards increases in rainfall intensity, 2 , 58 with recent increases in intensity exceeding those in other regions in the contiguous United States. Further increases in rainfall intensity are expected, 3 with increases in precipitation expected during the winter and spring with little change in the summer. 4 Monthly precipitation in the Northeast is projected to be about 1 inch greater for December through April by end of century (2070–2100) under the higher scenario (RCP8.5). 4

Sensitivity to projected changes in winter climate varies geographically, and venues are adapting by investing in artificial snowmaking, opening higher-elevation trails, and offering a greater range of activities and services. 115 , 117 As the margin for an economically viable winter recreation season (a season with more than 100 days for skiing; more than 50 for snowmobiling) shifts northward and toward higher elevations, some affected areas will be able to extend their seasons with artificial snowmaking. However, the capacity of some vulnerable southern and low-elevation locations to adapt in the long term is expected to be limited by warming nighttime temperatures. 115 , 116 , 119 Markets farther north may benefit from a greater share of regional participation depending on recreationist preferences like travel time 118 , 120 and perceived snow cover conditions informed by local weather, referred to as the backyard effect. 121

The Northeast winter recreation industry is an important economic resource for rural areas, supporting approximately 44,500 jobs and generating between $2.6–$2.7 billion in revenue annually. 115 , 116 Like other outdoor tourism industries, it is strongly influenced by weather and climate, making it particularly vulnerable to climate change. 116 , 117 , 118 Even under the lower scenario (RCP4.5), the average length of the winter recreation season and the number of recreational visits are projected to decrease by mid-century. 118 Under the same scenario, lost time for snowmaking is expected to delay the start of the ski season across southern areas, potentially impacting revenues during the winter holiday season. Activities that rely on natural snow and ice cover are projected to remain economically viable in only far northern parts of the region by end of century under the higher scenario (RCP8.5). 117 , 118

As Northeast winters warm, scenarios project a combination of less early winter snowfall and earlier snowmelt, leading to a shorter snow season. 104 , 105 The proportion of winter precipitation falling as rain has already increased and will likely continue to do so in response to a northward shift in the snow–rain transition zone projected under both lower and higher scenarios (RCP4.5 and RCP8.5). 106 , 107 , 108 The shift in precipitation type and fewer days below freezing 3 , 4 , 35 are expected to result in fewer days with snow on the ground; decreased snow depth, water equivalent, and extent; an earlier snowmelt; 105 , 109 , 110 and less lake ice. 111 Warming during the winter–spring transition has already led to earlier snowmelt-related runoff in areas of the Northeast with substantial snowpack (Figure 18.2). 112 Earlier snowmelt-related runoff and lower spring peak streamflows in these areas are expected in the 2041–2095 period compared with the 1951–2005 period. 105

On the other hand, the impacts of warming on forests and ecosystems during the summer and autumn are less well understood. 98 In the summer, flowering in many agricultural crops and tree fruits is regulated in part by nighttime temperature, and growers risk lower yields as these temperatures rise. 35 Warmer autumn temperatures 98 influence processes such as leaf senescence (the change in leaf color as photosynthesis ceases), fruit ripening, insect phenology, 35 and the start of bird migration and animal hibernation. 99 October temperatures are the best predictor of leaf senescence in the northern hemisphere, 100 but other climatic factors can also shift the timing of autumn processes. Agricultural drought can advance leaf coloring and leaf drop, while abundant soil moisture can delay senescence. 101 , 102 Early frost events or strong winds can also result in sudden leaf senescence and loss. 98 Many deciduous trees are projected to experience an overall increase in their amount of autumn foliage color. 103

Shorter, more moderate winters will present new challenges for rural industries. Poor surface and road conditions or washout have the potential to limit future logging operations, which need frozen or snow-covered soils to meet environmental requirements for winter operations. 70 , 88 Maple syrup production is linked to climate through potential shifts in sugar maple habitat, 89 tapping season timing and duration, 90 , 91 and the quality of both the trees and sap. 92 , 93 Climate change is making sugar maple tapping more challenging by increasing variability within and between seasons. Research into how the industry can adapt to these changes is ongoing. 89 , 94 , 95 With changes in weather and ecology come shifts in the cultural relationships to seasons as they have historically existed. Indigenous women from across these northeastern forests have come together to protect and sustain cultural traditions of the land they call Maple Nation. These climate impacts not only threaten the maple tree itself but also the seeds, soil, water, plants, and cultural lifeways that Indigenous peoples and tribal nations in the region associate with them. 96 , 97

Shifting seasonality can also negatively affect the health of forests ( Ch. 6: Forests, KM 1 ) and wildlife, thereby impacting the rural industries dependent upon them. Warmer winters will likely contribute to earlier insect emergence 74 and expansion in the geographic range and population size of important tree pests such as the hemlock woolly adelgid, emerald ash borer, and southern pine beetle. 75 , 76 , 77 Increases in less desired herbivore populations are also likely, with white-tailed deer and nutria (exotic South American rodents) already being a major concern in different parts of the region. 78 According to State Farm Insurance, 79 motorists in West Virginia and Pennsylvania are already the first and third group of claimants most likely to file an insurance claim that is deer-related. Erosion from nutria feeding in lower Eastern Shore watersheds of Maryland has resulted in widespread conversion of marsh to shallow open water, changing important ecosystems that can buffer against the adverse impacts from climate change. 80 Species such as moose, which drive a multimillion-dollar tourism industry, are already experiencing increased parasite infections and deaths from ticks. 81 , 82 , 83 Warmer spring temperatures are associated with earlier arrivals of migratory songbirds, 84 while birds dependent upon spruce–fir forests in the northern and mountainous parts of the region are already declining and especially vulnerable to future change. 85 Northern and high-elevation tree species such as spruce and fir are among the most vulnerable to climate change in the Northeast. 70 , 86 , 87

While unusual winter or early-spring warmth has caused plants to start growing and emerge from winter dormancy earlier in the spring, the increased vulnerability of species to subsequent cold spells is yet unknown. Early emergence from winter dormancy causes plants to lose their tolerance to cold temperatures and risk damage by temperatures they would otherwise tolerate. Early budbreak followed by hard freezes has led to widespread loss of fruit crops and reduced seasonal growth of native tree species in the Northeast. 35 , 73

Forests are already responding to the ongoing shift to a warmer climate, and changes in the timing of leaf-out affect plant productivity, plant–animal interactions, and other essential ecosystem processes. 69 , 70 Warmer late-winter and early-spring temperatures in the Northeast have resulted in trends towards earlier leaf-out and blooming, including changes of 1.6 and 1.2 days per decade, respectively, for lilac and honeysuckle ( Ch. 7: Ecosystems, Figure 7.3 ). 71 The increase in growing season length is partially responsible for observed increases in forest growth and carbon sequestration. 72

Seasonal differences in Northeast temperature have decreased in recent years as winters have warmed three times faster than summers. 3 By the middle of this century, winters are projected to be milder still, with fewer cold extremes, particularly across inland and northern portions of the Northeast. 3 This will likely result in a shorter and less pronounced cold season with fewer frost days and a longer transition out of winter into the growing season. 68 Under the higher scenario (RCP8.5), the trend of decreasing seasonality continues for the northern half of the region through the end of the century, but by then summer temperatures across the Mid-Atlantic are projected to rise faster than those in winter. 4

The distinct seasonality of the Northeast’s climate supports a diverse natural landscape adapted to the extremes of cold, snowy winters and warm to hot, humid summers. This natural landscape provides the economic and cultural foundation for many rural communities, which are largely supported by a diverse range of agricultural, tourism, and natural resource-dependent industries ( Ch. 10: Ag & Rural, KM 4 ). 1 The outdoor recreation industry contributes nearly $150 billion in consumer spending to the Northeast economy and supports more than one million jobs across the region. 64 Additionally, agriculture, fishing, forestry, and related industries together generate over $100 billion in economic activity annually, supporting more than half a million jobs in production and processing region-wide. 65 Projected changes in the Northeast’s seasons will continue to affect terrestrial and aquatic ecosystems, forest productivity, agricultural land use, and other resource-based industries. 1 Alpine, freshwater aquatic, and certain forest habitats are most at risk. 66 Without efforts to mitigate climate change, warming winters and earlier spring conditions under a higher scenario (RCP8.5) will affect native ecosystems and the very character of the rural Northeast. 67

The seasonality of the Northeast is central to the region’s sense of place and is an important driver of rural economies. Less distinct seasons with milder winter and earlier spring conditions are already altering ecosystems and environments in ways that adversely impact tourism, farming, and forestry. The region’s rural industries and livelihoods are at risk from further changes to forests, wildlife, snowpack, and streamflow.

Changing Coastal and Ocean Habitats, Ecosystem Services, and Livelihoods The Northeast’s coast and ocean support commerce, tourism, and recreation that are important to the region’s economy and way of life. Warmer ocean temperatures, sea level rise, and ocean acidification threaten these services. The adaptive capacity of marine ecosystems and coastal communities will influence ecological and socioeconomic outcomes as climate risks increase.

Ocean and coastal ecosystems are being affected by large changes in a variety of climate-related environmental conditions. These ecosystems support fishing and aquaculture,5 tourism and recreation, and coastal communities.6 They also provide important ecosystem services (benefits to people provided by the functions of various ecosystems), including carbon sequestration,147 wave attenuation,148,149 and fish150 and shorebird151 habitats. Observed and projected increases in temperature, acidification, storm frequency and intensity, and sea levels are of particular concern for coastal and ocean ecosystems, as well as local communities and their interconnected social and economic systems (Box 18.1). Ocean Warming Ocean and coastal temperatures along the Northeast Continental Shelf have warmed by 0.06°F (0.033°C) per year over the period 1982–2016 (Figure 18.4), which is three times faster than the 1982–2013 global average rate of 0.018°F (0.01°C) per year.39 Over the last decade (2007–2016), the regional warming rate has been four times faster than the long-term trend, with temperatures rising 0.25°F (0.14°C) per year (Figure 18.4). Variability in ocean temperatures over the Northeast Continental Shelf (see Figure 18.1 for the location) has been related to the northern position of the Gulf Stream, the volume of water entering from the Labrador Current, and large-scale background warming of the oceans.39,48,152,153 In addition to this warming trend, seasonality is also changing. Warming has been strongest during the summer months, and the duration of summer-like sea surface temperatures has expanded.154 In parts of the Gulf of Maine, the summer-like season lengthened by two days per year since 1982, largely due to later fall cooling; the summer-like period expanded less rapidly (about 1 day per year) in the Mid-Atlantic, primarily due to earlier spring warming.154

Figure 18.4: Change in Sea Surface Temperature on the Northeast Continental Shelf Two line graphs are shown. One is inset in the upper left corner of the other. The larger line graph shows the annual sea surface temperature (SST) changes (in degrees Fahrenheit) on the Northeast Continental Shelf over the period 1982 to 2016, compared to the 1982 to 2011 average. While annual SSTs have ranged from nearly 2 degrees below average to nearly 4 degrees above average over the period, a warming trend is evident, as described in the caption. The inset line graph shows SST differences from the 1982 to 2011 average as five-year rolling averages for summer and winter. Summer and winter SSTs have also warmed over the period, but the summer warming rate has been more pronounced in recent years. SHRINK

Figure 18.6: Changes in Distribution and Abundance of Marine Species Five line graphs are shown. The first graph illustrates changes in geographic distribution of the Atlantic cod, the American lobster, and the black sea bass along the Northeast Continental Shelf from 1970 to 2015. While all three species have shifted to more northerly latitudes, the shift is more pronounced for the American lobster and black sea bass. The remaining four graphs illustrate changes in biomass (in metric tons) of the Gulf of Maine-Georges Bank lobster, the Southern New England lobster, the Gulf of Maine cod, and the black sea bass. The Gulf of Maine cod and the Southern New England lobster stocks have declined in biomass to under 5,000 metric tons and under 500 metric tons, respectively. The stocks of Gulf of Maine-Georges Bank lobster and black sea bass have increased in biomass to more than 20,000 metric tons and more than 15,000 metric tons, respectively. SHRINK

Sea Level Rise, Storms, and Flooding Along the Mid-Atlantic coast (from Cape Hatteras, North Carolina, to Cape Cod, Massachusetts), several decades of tide gauge data through 2009 have shown that sea level rise rates were three to four times higher than the global average rate.46,205,206 The region’s sea level rise rates are increased by land subsidence (sinking)—largely due to vertical land movement related to the melting of glaciers from the last ice age—which leaves much of the land in this region sinking with respect to current sea level.47,207,208,209 Additionally, shorter-term fluctuations in the variability of ocean dynamics,210,211 atmospheric shifts,212,213 and ice mass loss from Greenland and Antarctica214 have been connected to these recent accelerations in the sea level rise rate in the region. For example, a slowdown of the Gulf Stream during a shorter period of extreme sea level rise observed over 2009–2010 has been linked to a weakening of the Atlantic meridional overturning circulation—the northward flow of upper-level warm, salty waters in the Atlantic (including the Gulf Stream current) and the southward flow of colder, deeper waters.215 These higher-than-average rates of sea level rise measured in the Northeast have also led to a 100%–200% increase in high tide flooding in some places, causing more persistent and frequent (so-called nuisance flooding) impacts over the last few decades.44,47,216,217 Coastal flood risks from storm-driven precipitation and surges are major drivers of coastal change218,219 and are also amplified by sea level increases.217,220,221 Storms have unique climatological features in the Northeast—Nor’easters (named for the low-pressure systems typically impacting New England and the Mid-Atlantic with strong northeasterly winds blowing from the ocean over coastal areas) typically occur between September and April, and when coupled with the Atlantic hurricane season between June and September, the region is susceptible to major storms nearly year-round. Storm flood heights driven by hurricanes in New York City increased by more than 3.9 feet (1.2 m) over the last thousand years.14 When coupled with storm surges, sea level rise can pose severe risks of flooding, with consequent physical and mental health impacts on coastal populations (see Key Messages 4 and 5). Landscape Change and Impacts on Ecosystems Services

Figure 18.7: Coastal Impacts of Climate Change A diagram shows present and possible future scenarios of a northeastern coastal landscape. In the present view, we are reminded that the coastal landscape provides a number of essential services to humans and to coastal species, including providing habitats and recreation. The possible future diagram shows how coastal landscapes will be impacted by storm activity and sea level rise in years to come. For example, forests and marshlands will either migrate inland or become submerged. Bluffs will erode, and barrier islands and beaches will migrate inland, narrow, or erode. And areas of development will require ongoing efforts to remain protected from coastal erosion and flooding. EXPAND

Forest Dieback Due to Sea Level Rise A photo shows an aerial view of the Bass River in New Jersey. The white pines bordering the river’s edge are dead, but their naked trunks remain standing. Further inland, a blend of healthy and dead pines is visible. EXPAND