Scholars@Duke
Jonathan Ryan

Jonathan Ryan CV

Assistant Professor of Ice and Climate Sciences
Earth and Climate Sciences
jonathan.ryan@duke.edu
Grainger Hall 3101, Durham, NC 27708
CV

Selected Publications

Contribution of surface and cloud radiative feedbacks to Greenland Ice Sheet meltwater production during 2002–2023

Journal Article Communications Earth and Environment · December 1, 2024 Greenland Ice Sheet meltwater runoff projections are essential for accurate forecasts of global sea-level rise. However, melt depends on complex interactions between climate warming, surface albedo, and clouds, which are challenging to simulate in models. ... Full text Cite

Community-scale changes to landfast ice along the coast of Alaska over 2000-2022

Journal Article Environmental Research Letters · February 1, 2024 Landfast sea ice that forms along the Arctic coastline is of great importance to coastal Alaskan communities. It provides a stable platform for transportation and traditional activities, protects the coastline from erosion, and serves as a critical habitat ... Full text Open Access Cite

Retreat of the Greenland Ice Sheet leads to divergent patterns of reconfiguration at its freshwater and tidewater margins

Journal Article Journal of Glaciology · January 1, 2024 Greenland's marine- and land-terminating glaciers are retreating inland due to climate warming, reconfiguring the way the ice sheet interacts with its proglacial environment. Here we use three decades of satellite imagery to determine whether the ice-sheet ... Full text Cite

Role of Snowfall Versus Air Temperatures for Greenland Ice Sheet Melt-Albedo Feedbacks

Journal Article Earth and Space Science · November 1, 2023 The Greenland Ice Sheet is a leading contributor to global sea-level rise because climate warming has enhanced surface meltwater runoff. Melt rates are particularly sensitive to air temperatures due to feedbacks with albedo. The primary melt-albedo feedbac ... Full text Cite

New proglacial meteorology and river stage observations from Inglefield Land and Pituffik, NW Greenland

Journal Article Geoscientific Instrumentation, Methods and Data Systems · September 22, 2023 Abstract. Meltwater runoff from the Greenland ice sheet (GrIS) is an important contributor to global sea level rise, but substantial uncertainty exists in its measurement and prediction. Common approaches for estimating ice sheet runoff are in situ ... Full text Cite

Proglacial river stage derived from georectified time-lapse camera images, Inglefield Land, Northwest Greenland

Journal Article Frontiers in Earth Science · June 9, 2023 The Greenland Ice Sheet is a leading source of global sea level rise, due to surface meltwater runoff and glacier calving. However, given a scarcity of proglacial river gauge measurements, ice sheet runoff remains poorly quantified. This lack of Full text Cite

Do Urban Golf Courses Provide Barriers to Equitable Greenspace Access in the United States?

Journal Article Annals of the American Association of Geographers · January 1, 2023 Providing equitable access to greenspace requires innovative strategies in urban areas where land is scarce and expensive. One potential solution is to make golf courses, which are often exclusive and require daily or annual membership fees, more accessibl ... Full text Cite

Direct measurement of optical properties of glacier ice using a photon-counting diffuse LiDAR

Journal Article Journal of Glaciology · December 2, 2022 The production of meltwater from glacier ice, which is exposed at the margins of land ice during the summer, is responsible for a large proportion of glacier mass loss. The rate of meltwater production from glacier ice is especially sensitive to its physic ... Full text Cite

Decreasing surface albedo signifies a growing importance of clouds for Greenland Ice Sheet meltwater production.

Journal Article Nature communications · July 2022 Clouds regulate the Greenland Ice Sheet's surface energy balance through the competing effects of shortwave radiation shading and longwave radiation trapping. However, the relative importance of these effects within Greenland's narrow ablation zone, where ... Full text Cite

Temporal Variability of Surface Reflectance Supersedes Spatial Resolution in Defining Greenland’s Bare-Ice Albedo

Journal Article Remote Sensing · December 23, 2021 Ice surface albedo is a primary modulator of melt and runoff, yet our understanding of how reflectance varies over time across the Greenland Ice Sheet remains poor. This is due to a disconnect between point or transect scale albedo sampling and the ... Full text Cite

Storage and export of microbial biomass across the western Greenland Ice Sheet.

Journal Article Nature communications · June 2021 The Greenland Ice Sheet harbours a wealth of microbial life, yet the total biomass stored or exported from its surface to downstream environments is unconstrained. Here, we quantify microbial abundance and cellular biomass flux within the near-surface weat ... Full text Cite

Hourly surface meltwater routing for a Greenlandic supraglacial catchment across hillslopes and through a dense topological channel network

Journal Article The Cryosphere · May 18, 2021 Abstract. Recent work has identified complex perennial supraglacial stream and river networks in areas of the Greenland Ice Sheet (GrIS) ablation zone. Current surface mass balance (SMB) models appear to overestimate meltwater runoff in these netwo ... Full text Cite

Supraglacial River Forcing of Subglacial Water Storage and Diurnal Ice Sheet Motion

Journal Article Geophysical Research Letters · April 16, 2021 Surface melting impacts ice sheet sliding by supplying water to the bed, but subglacial processes driving ice accelerations are complex. We examine linkages between surface runoff, transient subglacial water storage, and short-term ice motion from 168 cons ... Full text Cite

Human alteration of global surface water storage variability.

Journal Article Nature · March 2021 Knowing the extent of human influence on the global hydrological cycle is essential for the sustainability of freshwater resources on Earth1,2. However, a lack of water level observations for the world's ponds, lakes and reservoirs has limited t ... Full text Cite

Changes in sea ice travel conditions in Uummannaq Fjord, Greenland (1985–2019) assessed through remote sensing and transportation accessibility modeling

Journal Article Polar Geography · January 1, 2021 Shorefast sea ice provides an important platform for winter and spring travel between coastal Arctic communities unconnected by road networks. In the past two decades, local Arctic residents have reported thinning and earlier breakup of shorefast ice. Desp ... Full text Cite

GrSMBMIP: intercomparison of the modelled 1980–2012 surface mass balance over the Greenland Ice Sheet

Journal Article The Cryosphere · November 11, 2020 Abstract. Observations and models agree that the Greenland Ice Sheet (GrIS) surface mass balance (SMB) has decreased since the end of the 1990s due to an increase in meltwater runoff and that this trend will accelerate in the future. However, large ... Full text Cite

Global Characterization of Inland Water Reservoirs Using ICESat-2 Altimetry and Climate Reanalysis

Journal Article Geophysical Research Letters · September 16, 2020 Accurate, transparent knowledge of global reservoir levels is a prerequisite for effective management of water resources. However, no complete database exists because gauge data are not globally available and the current generation of satellite radar altim ... Full text Cite

Coldest Canadian Arctic communities face greatest reductions in shorefast sea ice

Journal Article Nature Climate Change · June 1, 2020 Shorefast sea ice comprises only about 12% of global sea-ice cover, yet it has outsized importance for Arctic societies and ecosystems. Relatively little is known, however, about the dominant drivers of its breakup or how it will respond to climate warming ... Full text Cite

Direct Observation of Winter Meltwater Drainage From the Greenland Ice Sheet

Journal Article Geophysical Research Letters · May 16, 2020 Meltwater runoff from the Greenland Ice Sheet (GrIS) significantly contributes to sea level rise and is the dominant driver of enhanced mass loss. While most melt occurs during summer, little is known about its seasonal and/or interannual retention within ... Full text Cite

Evaluation of CloudSat's Cloud-Profiling Radar for Mapping Snowfall Rates Across the Greenland Ice Sheet

Journal Article Journal of Geophysical Research: Atmospheres · February 27, 2020 The Greenland Ice Sheet is now the single largest cryospheric contributor to global sea-level rise yet uncertainty remains about its future contribution due to complex interactions between increasing snowfall and surface melt. Reducing uncertainty in futur ... Full text Cite

Glacier algae accelerate melt rates on the south-western Greenland Ice Sheet

Journal Article The Cryosphere · January 29, 2020 Abstract. Melting of the Greenland Ice Sheet (GrIS) is the largest single contributor to eustatic sea level and is amplified by the growth of pigmented algae on the ice surface, which increases solar radiation absorption. This biological albedo-red ... Full text Cite

Greenland Ice Sheet surface melt amplified by snowline migration and bare ice exposure.

Journal Article Science advances · March 2019 Greenland Ice Sheet mass loss has recently increased because of enhanced surface melt and runoff. Since melt is critically modulated by surface albedo, understanding the processes and feedbacks that alter albedo is a prerequisite for accurately forecasting ... Full text Cite

Arctic-Boreal Lake Dynamics Revealed Using CubeSat Imagery

Journal Article Geophysical Research Letters · February 28, 2019 Fine-scale, subseasonal fluctuations in Arctic-Boreal surface water reflect regional water balance and modulate trace gas emissions to the atmosphere but have eluded detection using traditional satellite remote sensing. We use high-resolution (~3–5 m), hig ... Full text Cite

Structural glaciology of Isunguata Sermia, West Greenland

Journal Article Journal of Maps · November 13, 2018 Full text Cite

Rapid Surface Lowering of Benito Glacier, Northern Patagonian Icefield

Journal Article Frontiers in Earth Science · May 1, 2018 Full text Cite

Meltwater storage in low-density near-surface bare ice in the Greenland ice sheet ablation zone

Journal Article Cryosphere · March 21, 2018 We document the density and hydrologic properties of bare, ablating ice in a mid-elevation (1215 m a.s.l.) supraglacial internally drained catchment in the Kangerlussuaq sector of the western Greenland ice sheet. We find low-density (0.43-0.91 g cm-3, μ Co ... Full text Cite

Dark zone of the Greenland Ice Sheet controlled by distributed biologically-active impurities.

Journal Article Nature communications · March 2018 Albedo-a primary control on surface melt-varies considerably across the Greenland Ice Sheet yet the specific surface types that comprise its dark zone remain unquantified. Here we use UAV imagery to attribute seven distinct surface types to observed albedo ... Full text Cite

A Full‐Stokes 3‐D Calving Model Applied to a Large Greenlandic Glacier

Journal Article Journal of Geophysical Research: Earth Surface · March 2018 AbstractIceberg calving accounts for around half of all mass loss from both the Greenland and Antarctic ice sheets. The diverse nature of calving and its complex links to both internal dynamics and climate make it challengi ... Full text Cite

Direct measurements of meltwater runoff on the Greenland ice sheet surface.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · December 2017 Meltwater runoff from the Greenland ice sheet surface influences surface mass balance (SMB), ice dynamics, and global sea level rise, but is estimated with climate models and thus difficult to validate. We present a way to measure ice surface runoff direct ... Full text Cite

Algae Drive Enhanced Darkening of Bare Ice on the Greenland Ice Sheet

Journal Article Geophysical Research Letters · November 28, 2017 Surface ablation of the Greenland ice sheet is amplified by surface darkening caused by light-absorbing impurities such as mineral dust, black carbon, and pigmented microbial cells. We present the first quantitative assessment of the microbial contribution ... Full text Cite

How robust are in situ observations for validating satellite-derived albedo over the dark zone of the Greenland Ice Sheet?

Journal Article Geophysical Research Letters · June 28, 2017 Calibration and validation of satellite-derived ice sheet albedo data require high-quality, in situ measurements commonly acquired by up and down facing pyranometers mounted on automated weather stations (AWS). However, direct comparison between ground and ... Full text Cite

UAV photogrammetry and structure from motion to assess calving dynamics at Store Glacier, a large outlet draining the Greenland ice sheet

Journal Article The Cryosphere · January 6, 2015 Abstract. This study presents the application of a cost-effective, unmanned aerial vehicle (UAV) to investigate calving dynamics at a major marine-terminating outlet glacier draining the western sector of the Greenland ice sheet. The UAV was flown ... Full text Cite