Recipient Organization
RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY
3 RUTGERS PLZA
NEW BRUNSWICK,NJ 08901-8559
Performing Department
Marine and Coastal Sciences
Non Technical Summary
Climate change and how people respond to it could arguably be the most important issues of the 21st century. The global surface temperature in 2020 was essentially tied with 2016 as the warmest year in the instrumental temperature record going back to 1880 (GISTEMP Team, 2021). As global temperatures inexorably increase amid a multitude of other interconnected and changing climate phenomena, human societies will be faced with critical choices to maintain the stability of natural and social systems at local, national, and global scales. Today, climate is changing most rapidly at the highest northern latitudes because of the strong positive feedbacks there (e.g., ice albedo, water vapor, clouds). Although changing less rapidly than the Arctic, the Antarctic is also changing, and the large reservoir of ice on that continent has major implications for sea-level rise later this century. In addition to the changes themselves in these polar regions, there are potential impacts of these changes on weather and climate at lower latitudes. The overall focus of this project is to improve our understanding of climate change and the critical processes and feedbacks in the climate system, with a particular emphasis on polar regions and their linkages with lower latitudes.This research will improve our understanding of how climate is changing and is projected to change during the next few decades and through the end of this century. Potential changes in the frequency of extreme weather events, such as storms, fires, floods, and droughts as well as more gradual changes such as sea-level rise and sea-ice retreat will have significant societal impacts locally, nationally, and globally. Among the potential impacts are those on (1) agriculture and global food systems as they are forced to respond to changes in the frequency of droughts and floods, (2) natural resources and ecosystems owing to more fires and extreme heat and precipitation events, and (3) coastal communities responding to a rising sea and increased incidents of storm surge flooding and salt water intrusion into local water systems. These impacts are already being felt, and the ultimate level of impact will depend on how much the climate will change over the next few decades and throughout this century. The proposed research will help to address such questions by improving our understanding of how climate will change in the future, both at regional and global scales.
Animal Health Component
10%
Research Effort Categories
Basic
80%
Applied
10%
Developmental
10%
Goals / Objectives
The overarching goal of this proposal is to better understand how climate will changeduring the 21stcentury, with a particular emphasis onunderstanding the critical processes and feedbacks that contribute to these changesas well ason thesimilarities, differences andlinkages between polar regions and lower latitudes. Thiswill be accomplished by investigating the followingthreeobjectives:Objective 1.Determine howhydrologic processes inhighnorthernterrestrial systemswillrespond toglobal warming and how these hydrologic changeswill in turnaffect the rate of climate change, with an additional focus on the effects of elevation.Objective 2.Determine howpolar climates are projected tochangeduring this century, with an emphasis on changes insea-ice extent, andhowprojected futurechanges in sea iceare related to changes in their adjacentterrestrial systemsas well as withlower latitudes.Objective 3.Synthesize theinter-relatedresults obtained for each of the othertwoobjectives toidentify the roles of differentfeedbacks and processesincausingclimate change in polarregions as well as to understand the linkages between climate change in polar and lower latitude regions.
Project Methods
Objective 1: Global climate model output from multiple climate models and multiple model simulations will be used to continue to examine high latitude regions in the Arctic terrestrial system in both North America and in Russia. The focus of our recent paper (Miller et al., 2021) has been on 21st century high-latitude warming in eastern Siberia. This work will be extended to determine projected changes of various hydrologic variables through the 21st century north of 50oN. This region encompasses all of the major river systems that flow into the Arctic Ocean including the Mackenzie River in Canada and the Ob, Yenesei, Lena, and Kolyma rivers in Russia. Model output will be obtained from the CMIP5 and CMIP6 data portals, much of which has already been downloaded. Among the specific hydrologic variables to be examined are precipitation, soil moisture, snow cover, atmospheric water vapor, permafrost, and clouds. In addition, we will examine changes in river discharge into the Arctic Ocean for models that include that variable. We will determine whether changes and trends in these variables are statistically significant.Some of our preliminary analysis indicates that precipitation is projected to increase throughout much of this high-latitude region. We will investigate whether these projected changes vary with season, with elevation, and with latitude. Another aspect of precipitation is how much of it falls as rain and how much as snow. We expect that the ratio of snow to rain during precipitation events will decrease as the climate warms later this century. Snowpack provides an important reservoir of freshwater during winter and then affects soil moisture and river discharge in the spring and early summer. Melting permafrost has implications for built infrastructure, for the hydrologic cycle, and for the potential release of methane, a powerful greenhouse gas. We will use model output to assess changes in ground temperatures and assess changes in the depth of the active layer (the ground layer that remains unfrozen for part of the year). This layer is expected to deepen as the climate warms.Objective 2. : This objective will be achieved primarily using the GLORYS ocean reanalysis in conjunction with the atmospheric reanalyses ERA5 and MERRA to examine changes in the Arctic Ocean during the last 25 years. We will calculate ocean heat budgets and freshwater storage during the last three to five decades, primarily in the Beaufort Gyre region northwest of Canada where freshwater from river discharge and inflow through the Bering Strait accumulates. Periodically, the atmospheric circulation changes and significant quantities of freshwater are released from the gyre, some of which ultimately is exported through Fram Strait into the North Atlantic Ocean where it can affect the overturning circulation there. We have used a particle tracking method to identify freshwater pathways in the Arctic. Our preliminary analysis indicates that the freshwater pathways of the Mackenzie River and Bering Strait inflow were quite anomalous in 2007, and in part, contributed to record summer sea-ice retreat that year. We plan to continue this investigation using a higher resolution version of the GLORYS ocean reanalysis and completing an analysis of the heat budgets following the freshwater discharge plumes. Among the other factors affecting Arctic freshwater storage and summer sea-ice extent that will be considered as part of the proposed research are storms, atmospheric circulation, precipitation, and ocean processes. In the southern hemisphere we plan to expand on our recent research on the rapid warming at the South Pole to better understand the local forcing as well as the far-field forcing through tropical Pacific teleconnections.One of the important questions related to the local forcing there is how much of the increasing temperature is related directly to advection of heat rather than changes in other variables (e.g., water vapor or clouds) that affect the local energy budgets.Objective 3: The global hydrologic cycle is a complex and important component of the climate system. To explain past climate changes and to predict manifestations of increasing future concentrations of greenhouse gases, it is necessary to understand the complex interactions and feedbacks between the hydrologic cycle and the overall climate system. Goose et al. (2018) have reviewed climate feedbacks in polar regions, many of which we will address in this research. We will also investigate linkages between polar regions and lower latitudes (e.g., connections between the tropical Pacific Ocean and the Arctic and Antarctica).One of the climate variables that links hydrologic changes to temperature change is snow cover. Positive temperature anomalies lead to decreased snow cover and a reduction in surface albedo which in turn leads to increased absorption of solar radiation and increased surface warming. This positive feedback is one of the strongest feedbacks in the climate system, and we will investigate its contribution to future enhanced warming, both over land and over the ocean. Other positive feedbacks on winter temperatures include increases in cloud cover and water vapor that increases downward longwave radiation (Chen et al. 2003; Miller et al., 2007; Cao et al. 2017). Each of these three variables, snow cover, clouds, and water vapor, and their interactions with each other and with temperature will be examined, and statistically significant trends in these variables will be identified. The radiative properties and distribution of clouds remain arguably the most difficult part of the climate system to simulate at the resolutions of global climate models. Our analysis will examine trends in cloud cover as well as other cloud properties where they are available, including cloud optical thickness and cloud height. Another connection between the first two objectives is to understand how projected changes in terrestrial Arctic hydrologic systems can potentially affect the Arctic Ocean, in particular changes in sea ice. We will continue to investigate elevation dependent warming (EDW) in high-latitude river basins in North America and Russia because these changes in terrestrial systems will affect the hydrologic cycle and freshwater input to the Arctic Ocean, which in turn can affect sea-ice cover. We will examine changes in freshwater and heat content at the mouth of Arctic river systems to assess their impact on Arctic climate. There are potential two-way linkages here as noted in studies that suggest that changes in Arctic sea ice can affect mid-latitude climate (Francis and Vavrus, 2012, 2015; Cohen et al., 2019; Li et al., 2020) while a model study by England et al. (2020) finds that changes in both Arctic and Antarctic sea ice can affect tropical climate as well. These potential linkages are still areas of active research, and the science remains controversial as noted in a model study by Blackport and Screen (2020). Our recent work links tropical sea-surface temperature anomalies to the South Pole warming (Clem et al., 2019, 2020), and we plan to do a more comprehensive analysis of the Antarctic energy budget using atmospheric reanalyses. For the Arctic Ocean, we will employ particle trajectory analysis to determine whether freshwater pathways of input plumes are changing, and if so, how and why, and furthermore what are the implications for Arctic sea ice. Our preliminary analysis indicates that the pathway of Mackenzie River plumes shifted from generally eastward through the Canadian Archipelago prior to 2007 to directly northward into the Beaufort Gyre and was partially responsible for the anomalous sea-ice retreat in 2007.