David Fisher

• PhD
• Professor (adjunct) at University of Ottawa

Knowledge of Antarctic permafrost is mainly derived from the Antarctic Peninsula and Victoria Land. This study examines the 2019–2023 temperature and humidity conditions, distribution and development of polygonal terrain and the origin of ground ice in soils of the Untersee Oasis. In this region, the surface offset (MAAT ≅ MAGST) and the thermal of...

Surface height changes above three previously undetected subglacial lakes in northeastern Greenland are documented using CryoSat, DEMs and ICESat-2. Between 7 February and 6 March 2012, the central ice region (22.6 km ² ) above the largest lake dropped by ~37 m followed by a further drop of 12 m in the following 29 days. This implies a subglacial w...

Here, we present a compilation of 95 ice temperature profiles from 85 boreholes from the Greenland ice sheet and peripheral ice caps, as well as local ice caps in the Canadian Arctic. Profiles from only 31 boreholes (36 %) were previously available in open-access data repositories. The remaining 54 borehole profiles (64 %) are being made digitally...

Here, we present a compilation of 85 ice temperature profiles from 79 boreholes from the Greenland Ice Sheet and peripheral ice caps, as well as local ice caps in the Canadian Arctic. Only 25 profiles (32 %) were previously available in open-access data repositories. The remaining 54 profiles (68 %) are being made digitally available here for the f...

We use the freezing point depressing magnesium and calcium perchlorates in Martian regolith to redistribute ground ice by residual liquid water migration following the initial emplacement of ground ice by vapour deposition. This residual liquid water is moved by forces generated by periodic surface temperatures that decay with depth in conjunction...

Global warming and permafrost degradation are impacting landscapes, ecosystems and the climate-carbon system. Current ground ice and geohazard maps rely on the frost susceptibility of surficial sediments, and substantial areas underestimate ice abundance. Here we use a soil environmental model to show the importance of considering unfrozen water co...

Climate change is impacting lakes and ponds in Antarctica. To that end, we investigated the distribution and chemical composition of ice-covered ponds in Untersee Oasis, East Antarctica. Thirty-nine ponds were inventoried, and the thirteen sampled ponds have low total dissolved solutes (TDS) with a Ca(Na)-SO4 or Na-Cl geochemical facies. Tritium an...

Over the past few decades, the δ¹⁸O records of ice wedges have been used to estimate late Quaternary winter air temperatures. This study first reviews the development of ice wedges and the potential isotopic fractionation that takes place from snow deposition to formation of ice veinlets. Then, based on the high resolution analysis of ice wedges fr...

Ice wedges are ubiquitous periglacial features in permafrost terrain. This study investigates the timing of ice wedge formation in the Fosheim Peninsula (Ellesmere and Axel Heiberg Islands). In this region, ice wedge polygons occupy ~50% of the landscape, the majority occurring below the marine limit in the Eureka Sound Lowlands. Numerical simulati...

The origin and stability of ground ice in the stable uplands of the McMurdo Dry Valleys remains poorly understood, with most studies focusing on the near-surface permafrost. The 2016 Friis Hills Drilling Project retrieved five cores reaching 50 m depth in mid-Miocene permafrost, a period when Antarctica transitioned to a hyper-arid environment. Thi...

We examine how recent increases in air temperature and precipitation, together with reductions in sea ice extent, may have affected the regional δD–δ¹⁸O composition of precipitation. In spring 2014, 80 snow samples were collected from six glaciers and ice caps across the Queen Elizabeth Islands, and in 2009 and 2014, two shallow ice cores were coll...

We present the basic theory of stable isotopes (δ(18O) and δ(D)) of freezing water solutions in the environment set within a water isotope‐augmented version of FREZCHEM(V15). We validate this model with a couple of examples. The isotope‐capable FREZCHEM is simplified to run much faster using set‐piece initial chemistries to calculate the freezing t...

Perennially ice-covered lakes that are tightly sealed from the atmosphere represent a unique group of polar lakes. In these lakes, the δD-δ¹⁸O evolution of the water column and steady-state conditions are controlled by rates of recharge and freezing at the bottom of the ice cover. We developed a recursive model (FREEZCH9) that takes into account th...

Knowledge of the amount of unfrozen water and its migration in permafrost soils is important for understanding physico‐chemical and biological processes. Here, we developed sub‐routines in FREZCHEM and embedded them in the WATEREGO2 soil environmental model to: (a) estimate unfrozen water content under changing soil temperatures and water–ice phase...

Lake Untersee is one of the largest perennially ice-covered lakes in Dronning Maud Land. We investigated the energy and water mass balance of Lake Untersee to understand its state of equilibrium. The thickness of the ice cover is strongly correlated with sublimation rates; variations in sublimation rates across the ice cover are largely determined...

Lake Untersee is one of the largest perennially ice-covered lakes in Dronning Maud Land. We investigated the energy and water mass balance of Lake Untersee to understand its state of equilibrium. The thickness of the ice cover is strongly correlated with sublimation rates; variations in sublimation rates across the ice cover are largely determined...

The Holocene, which currently spans ~11 700 years, is the shortest series/epoch within the geological time scale (GTS), yet it contains a rich archive of evidence in stratigraphical contexts that are frequently continuous and often preserved at high levels of resolution. On 14 June 2018, the Executive Committee of the International Union of Geologi...

The Holocene Series/Epoch is the most recent series/epoch in the geological timescale, spanning the interval from 11,700 yr to the present day. Together with the subadjacent Pleistocene, it comprises the Quaternary System/Period. The Holocene record contains diverse geomorphological, biological, climatological and archaeological evidence, within se...

The Holocene is probably the most intensively studied series/epoch within the geological record, and embodies a wide array of geomorphological, climatic, biotic and archaeological evidence; yet little attention has hitherto been paid to a formal subdivision of this series/epoch. Here we report a tripartite division of the Holocene into the Greenlan...

The Laurentide Ice Sheet (LIS) occupied a large part of North-America during the late Pleistocene. Determining the proper surface geometry and elevation of the LIS is of central importance to estimate global changes in sea-level and atmospheric circulation patterns during the late Pleistocene and Holocene. Despite largely disappearing from the land...

Black carbon aerosol (BC), which is emitted from natural and anthropogenic sources (e.g., wildfires, coal burning), can contribute to magnify climate warming at high latitudes by darkening snow- and ice-covered surfaces, and subsequently lowering their albedo. Therefore, modeling the atmospheric transport and deposition of BC to the Arctic is impor...

When making multi-proxy reconstructions over Holocene-long periods, an argument is presented that the elevation of the sites used and/or their elevation history must be taken into account before their proxy records (of temperature or precipitation) are included in the reconstruction. It is shown that to ignore elevation, results in first order erro...

The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in ae...

The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in ae...

Antarctica is an important region where we can improve our understanding of physico-chemical and biological processes in extreme cold and dry environments. Despite Canada not having a formal Antarctic research program, scientists in Canada have been actively involved in multi-disciplinary Antarctic permafrost research for several decades. Research...

Little is known about the abundance and source of soil organic carbon and biogeochemical cycling in permafrost soils from the ultraxerous environment of the Dry Valleys of Antarctica. Here, we investigate the distribution, source and cycling of organic carbon, total nitrogen and carbonates in the icy permafrost soils of University Valley, Quarterma...

Significance Reconstructions of past environmental changes are important for placing recent climate change in context and testing climate models. Periods of past climates warmer than today provide insight on how components of the climate system might respond in the future. Here, we report on an Arctic climate record from the Agassiz ice cap. Our re...

Ground ice is one of the most important and dynamic geologic components of permafrost; however, few studies have investigated the distribution and origin of ground ice in the McMurdo Dry Valleys of Antarctica. In this study, ice-bearing permafrost cores were collected from 18 sites in University Valley, a small hanging glacial valley in the Quarter...

In the upper McMurdo Dry Valleys, 90% of the measured ice table depths range from 0 to 80 cm; however numerical models predict that the ice table is not in equilibrium with current climate conditions and should be deeper than measured. This study explored the effects of boundary conditions (air vs ground surface temperature and humidity), ground te...

In this synthesis paper, we summarize published records showing the spatial and temporal pattern of climate change through the Holocene in Arctic Canada and Greenland. Our synthesis includes 47 records from a recently published database of highly resolved, quantitative Holocene climate records from the Arctic (Sundqvist et al., 2014). We plot the t...

Past emissions of the toxic metal mercury (Hg) persist in the global environment, yet these emissions remain poorly constrained by existing data. Ice cores are high-resolution archives of atmospheric deposition that may provide crucial insight into past atmospheric Hg levels during recent and historical time. Here we present a record of total Hg (H...

Continuous, high-resolution paleoclimate records from the North Pacific region spanning the past 1500 years are rare, and the behavior of the Aleutian Low (ALow) pressure center, the dominant climatological feature in the Gulf of Alaska, remains poorly constrained. Here we present a continuous, 1500 year long, calibrated proxy record for the streng...

This proposal, by a Working Group of Integration of ice-core, marine, and terrestrial records (INTIMATE) and the Subcommission on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS), is for a formal subdivision of the Holocene Series/Epoch. Although previous attempts to subdivide the Holocene have proved inconclusive...

A major achievement in research supported by the Kluane Lake Research Station was the recovery, in 2001 – 02, of a suite of cores from the icefields of the central St. Elias Mountains, Yukon, by teams of researchers from Canada, the United States, and Japan. This project led to the development of parallel, long (103 – 104 year) ice-core records of...

This study investigates the origin and age of ground ice in the uppermost 1 m of permafrost in University Valley, one of the upper valleys in the McMurdo Dry Valleys of Antarctica. In contrast to other regions in the MDV, mean daily air and soil temperatures at the coring sites are always below 0 �C, which allows for unique cryogenic processes to o...

Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling (‘NEEM’) ice core a...

This discussion paper, by a Working Group of INTIMATE (Integration of ice-core, marine and terrestrial records) and the Subcommision on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS), considers the prospects for a formal subdivision of the Holocene Series/Epoch. Although previous attempts to subdivide the Holoce...

At latitude 67°N, Penny Ice Cap on Baffin Island is the southernmost large ice cap in the Canadian Arctic, yet its past and recent evolution is poorly documented. Here we present a synthesis of climatological observations, mass balance measurements and proxy climate data from cores drilled on the ice cap over the past six decades (1953 to 2011). We...

Recent melt rates of Canadian Arctic ice caps are the highest in four millennia, Global and Planetary Change (2011), doi: 10.1016/j.gloplacha.2011.06.005 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will underg...

Ice cores were recently used to infer elevation changes of the Greenland ice sheet (GrIS) throughout the Holocene [Vinther et al., Nature, 461, 2009]. A key component of the analysis involved removing the vertical land motion signal from δ18O records. To improve on the original analysis, a geophysical modeling approach is used here to determine mor...

Arctic sea ice extent is now more than two million square kilometres less than it was in the late twentieth century, with important consequences for the climate, the ocean and traditional lifestyles in the Arctic. Although observations show a more or less continuous decline for the past four or five decades, there are few long-term records with whi...

The δ(18O) Holocene of the Mt Logan ice core is very different from those of eastern Arctic Canada and Greenland. The large changes seen in Logan dwarf even the largest change (the cooling event 8200 years ago) in the Atlantic-sector cores. Large changes in Logan’s δ(18O) and d are related to the state of El Niño as reflected by the Quelccaya δ(18O...

The study of ancient massive ground ice and sediment-rich ice bodies not only allows an understanding of the stability of permafrost, but also offers the possibility to understand the long-term preservation and viability of microbes within these ice bodies. Although microorganisms have been identified in ancient bodies of ground ice and permafrost,...

Study of two cores through an ice cap on northern Ellesmere Island suggests (1) during the Wisconsin Glaciation the ice near the crest was never more than about 200 m thicker than at present; (2) in a preceding glaciation, the ice was thicker than this, and the local ice divide near the boreholes was eliminated; (3) early in the Sangamon Interglaci...

A high-resolution, 8000 year-long ice core record from the Mt. Logan summit plateau (5300 m asl) reveals the initiation of trans-Pacific lead (Pb) pollution by ca. 1730, and a >10-fold increase in Pb concentration (1981-1998 mean = 68.9 ng/l) above natural background (5.6 ng/l) attributed to rising anthropogenic Pb emissions from Asia. The largest...

DOI: 10.1029/2009JE003415 The Phoenix and Mars Reconnaissance Orbiter (MRO) missions collaborated in an unprecedented campaign to observe the northern polar region summer atmosphere throughout the Phoenix mission (25 May to 2 November 2008; Ls = 76°-150°) and slightly beyond (∼Ls = 158°). Five atmospherically related campaigns were defined a priori...

The Phoenix Mars Lander detected a larger number of short (∼20 s) pressure drops that probably indicate the passage of convective vortices or dust devils. Near-continuous pressure measurements have allowed for monitoring the frequency of these events, and data from other instruments and orbiting spacecraft give information on how these pressure eve...

The Phoenix Wet Chemistry Lab (WCL) discovered substantial amounts of magnesium, calcium, and sodium perchlorate in the soil of polar Mars. Magnesium perchlorate is likely the dominant salt in the polar region's soils. But it could be that the cations are contributed by a mixture of Mg, Ca, and Na. Mg, Ca, and Na perchlorate brines can stay liquid...

The element Plutonium was artificially produced during the 1940’s and was made known through the detonation of “atomic” bombs. Prior to this time, this element was not detectable in the environment. Since then, through the development of technology, the existence of Pu in the biosphere, hydrosphere, atmosphere, etc. can be determined with ease. Thu...

Entering an era of global warming, the stability of the Greenland ice sheet (GIS) is a major concern, especially in the light of new evidence of rapidly changing flow and melt conditions at the GIS margins. Hence it is imperative to advance our understanding of GIS dynamics by studying the response of the GIS to past climatic change. In this study...

The relationship between tropical Pacific processes (e.g., El Nino Southern Oscillation; ENSO) and high latitude climate on a variety of timescales in the past remains a fundamental question, particularly with respect to any lead-lag associations during significant climate transitions. Several recent observational and modeling studies have document...

The Aleutian Low (ALOW) is a semi-permanent low pressure center that dominates the wintertime climate of the North Pacific, and is an integral component of major ocean-atmosphere climate oscillations including the Pacific Decadal Oscillation and the extra-tropical response to the El Niño-Southern Oscillation. Previous research has suggested that th...

The objective of the Phoenix mission is to determine if Mars' polar region can support life. Since liquid water is a basic ingredient for life, as we know it, an important goal of the mission is to determine if liquid water exists at the landing site. It is believed that a layer of Martian soil preserves ice by forming a barrier against high temper...

Despite its growing environmental significance, there are no detailed historical records of atmospheric As deposition for the Northern Hemisphere. Having overcome the severe analytical challenges in measuring As in polar ice, and using an Arctic ice core representing ˜16 ka of snow accumulation, we present a complete record of atmospheric As deposi...

On entering an era of global warming, the stability of the Greenland ice sheet (GIS) is an important concern, especially in the light of new evidence of rapidly changing flow and melt conditions at the GIS margins. Studying the response of the GIS to past climatic change may help to advance our understanding of GIS dynamics. The previous interpreta...

Phoenix Ascending The Phoenix mission landed on Mars in March 2008 with the goal of studying the ice-rich soil of the planet's northern arctic region. Phoenix included a robotic arm, with a camera attached to it, with the capacity to excavate through the soil to the ice layer beneath it, scoop up soil and water ice samples, and deliver them to a co...

Phoenix Ascending The Phoenix mission landed on Mars in March 2008 with the goal of studying the ice-rich soil of the planet's northern arctic region. Phoenix included a robotic arm, with a camera attached to it, with the capacity to excavate through the soil to the ice layer beneath it, scoop up soil and water ice samples, and deliver them to a co...

The NASA Phoenix mission to Mars landed on 25 May 2008 and operated for five months. The LIDAR instrument on Phoenix observed water ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground. Measurements of atmospheric dust indicat...

The Phoenix Mars Lidar instrument observed that atmospheric dust is well mixed up to a height of 4 km. The lidar also observed that water ice clouds form within the PBL each night in late summer and that ice crystals precipitate toward the surface.

The north cap of Mars has basal temperature that precludes the flow of ice. Phoenix discovered polar soils contain perchlorate salts. These salts depress the melting point so it could form a sludge that provides a mobile bed that moves the ice outwards.

The Phoenix and MRO spacecraft performed coordinated/simultaneous observations of the martian atmosphere to capture seasonal and diurnal variability.

Near continuous measurements of pressure and temperature by the MET instrumentation on the Phoenix Mars Lander are used to identify the passage of vertically oriented vortex structures at the Phoenix landing site (126W, 68N) on Mars.

The Phoenix landing site had two types of ice soil mixtures with variable purity. No spectral evidence for high concentration perchlorate brines was found from analysis of trench (e.g. no layering) and sublimation lag deposits.

Recent efforts to link the isotopic composition of snow in Greenland with meteorological and climatic parameters have indicated that relatively local information such as observed annual temperatures from coastal Greenland sites, as well as more synoptic scale features such as the North Atlantic Oscillation (NAO) and the temperature seesaw between J...

The Phoenix Mission excavated materials at the Phoenix Landing site using the Robotic Arm (RA) while materials in the trenches and in the talus piles were documented with the Surface Stereo Imager (SSI) using 15 filters with bands from 485-1005 nm. Two polygons (Humpty Dumpty and Wonderland) are in the workspace and have frozen ice/soils mixtures t...

A calibrated 1500 year-long glaciochemical proxy record for the strength of the wintertime (November-March) Aleutian Low (ALOW) from the Mt. Logan summit (PR Col; 5300 m a.s.l.) ice core [Na+] time series reveals a strong ALOW from ca. 650-900 A.D., ca. 1300-1550 A.D., and ca. 1700-1998 A.D., and a weaker ALOW from ca. 900-1300 A.D. and ca. 1550-17...

The Phoenix Mars lander (PHX) spacecraft and the Mars Reconnaissance Orbiter (MRO) have collaborated during the course of the Phoenix mission to simultaneously observe the same atmospheric column with a variety of instruments. PHX carries pressure and near-surface air temperature sensors, an upward-looking LIDAR that probes up to 20 km altitude, a...

The discovery of substantial amounts of magnesium and perchlorate by Phoenix' "Wet Chemistry Lab" (WCL) in the soil of Polar Mars suggests that magnesium perchlorate could be the dominant salt in the polar region's soils. This prospect opens some unexpected doors for moving liquid water around at temperatures as low as -68C. In its fully hydrated f...

Near continuous measurements of temperatures and pressure on the Phoenix Mars Lander are used to identify the passage of vertically oriented vortex structures at the Phoenix landing site (126W, 68N) on Mars. Observations: During the Phoenix mission the pressure and temperature sensors frequently detected features passing over or close to the lander...

The Phoenix mission has included several instruments for observing the atmosphere of Mars. The measurements include atmospheric temperature, pressure, wind, humidity, optical depth, composition, and imaging. A unique instrument on the Phoenix mission was a lidar that measured the backscatter of pulsed laser light emitted upward into the atmosphere....

Phoenix, the first Mars Scout mission, capitalizes on the large NASA investments in the Mars Polar Lander and the Mars Surveyor 2001 missions. On 4 August 2007, Phoenix was launched to Mars from Cape Canaveral, Florida, on a Delta 2 launch vehicle. The heritage derived from the canceled 2001 lander with a science payload inherited from MPL and 2001...

The Phoenix polar mission will land close to 68°N, 233°E in May 2008 at Ls ~ 75 and operate 90 sols until Ls ~ 125 with possible extension to Ls ~ 142. Phoenix Meteorology (MET), Thermal and Evolved Gas Analyzer (TEGA) and Microscopy, Electrochemistry and Conductivity Analyzer (MECA) instrument packages will measure the air's temperature, water vap...

As an introduction to this Icarus special issue for the 4th Mars Polar Science and Exploration Conference, we discuss five key questions in Mars polar science, gleaned from plenary discussions and presentations held at the conference. These questions highlight major unknowns in the field. (1) What are the physical characteristics of the polar layer...

Applying strict clean room techniques and sector field ICP-MS, a total of 567 ice and snow samples from Devon Ice Cap, Arctic Canada, have been analysed for silver (Ag) and thallium (Tl), providing a continuous record of atmospheric deposition of both elements for the past approximately 16,000 yr. Concentrations of Ag and Tl ranged from 0.02 to 5.8...

In this study, various approaches that can potentially distinguish between vapor- and liquid-derived ground ice in the martian regolith (petrography, geochemistry, stable OH isotopes, CO2O2N2Ar gas composition) are examined using terrestrial ground ice examples. Although the stable OH isotope composition ratios can distinguish between vapor- and li...

Four ice cores from the Agassiz ice cap in the Canadian high arctic and one ice core from the Renland ice cap in eastern Greenland have been synchronized to the Greenland Ice Core Chronology 2005 (GICC05) which is based on annual layer counts in the DYE-3, GRIP and NGRIP ice cores. Volcanic reference horizons, seen in electrical conductivity measur...

1] A high-resolution, 8000 year-long ice core record from the Mt. Logan summit plateau (5300 m asl) reveals the initiation of trans-Pacific lead (Pb) pollution by ca. 1730, and a >10-fold increase in Pb concentration (1981 – 1998 mean = 68.9 ng/l) above natural background (5.6 ng/l) attributed to rising anthropogenic Pb emissions from Asia. The lar...

1] Applying strict clean room procedures and sector field inductively coupled plasma mass spectrometry (ICP-MS) methods, concentrations of Sb and Sc were determined in 57 sections of a 170.6-m-long ice core drilled on Devon Island, Arctic Canada, in 1999, providing a record of atmospheric Sb extending back 15,800 years. Natural background concentra...