Summer 2004

NEW MEXICO’S CHANGING CLIMATE

The word climate refers to the long-term case. For example, Albuquerque and Los Ocean, whereas Albuquerque’s climate average and range of weather conditions Angeles are at nearly the same latitude, owes a great deal to its elevation above (the hourly or daily fluctuation of tem- but their climates are markedly different: sea level and its distance from any ocean perature, , , , Unlike Albuquerque, rarely with major mountain barriers in all direc- etc.) that prevail at any given place. experiences subfreezing temperatures and tions. If we can understand the link Although weather varies a great deal from between the boundary conditions and place to place, the processes responsible local temperature and precipitation, then for weather are the same. The atmo- we have some hope of predicting the spheric processes that cause an changes in climate associated with known individual , for example, or predicted changes in those boundary are fundamentally the same whether conditions. the storm occurs in , Alabama, or Argentina, but the average New Mexico’s Climate Today frequency and seasonal variability of Climatological “normal” conditions are are quite different in each defined rather arbitrarily as a 30-year of those places. Climate is most average measured over the most recent often described in terms of three decades. The statewide annual aver- temperature and precipitation. age temperature for 1961–1990 was Climate is determined by fixed 53.1°F (but that average is rising: the or slowly varying factors called 1971–2000 average was almost boundary conditions, which modu- 53.5°F). New Mexico’s temperature late weather. The primary factor is is considerably cooler than states to the intensity of sunlight, determined the east at the same latitude because by the brightness of the sun, Earth’s of the high average elevation of the state, orbital geometry, and latitude. Locations and the long distance from the in tropical latitudes receive a steady moderating effects of oceans in winter. A stream of high intensity sunlight year- smoothed map of annual average temper- round; polar latitudes actually receive atures shows the expected decrease of slightly more sunlight than the tropics in temperature from south to north, due to summer, but no sunlight at all in win- the gradient in the intensity of sunlight. ter. In addition to the sun’s radiation, Schematic map of the principal boundary conditions that Superimposed on that pattern, the Earth’s surface receives infrared radia- influence New Mexico’s climate. The sun currently sends low-lying Rio Grande valley appears as tion from the atmosphere above. The about 1368 Watts per square meter of radiation into a tongue of warm temperature intensity of infrared radiation Earth’s atmosphere. This “solar constant” is the amount of extending northward into the center received at the surface is determined radiant energy flowing each second from the sun into the of the state amidst cooler temperatures top of the atmosphere. by cloud cover, humidity, and the in high elevation regions ( atmospheric concentrations of infrared- receives most of its precipitation in win- Plateau, and the Sacramento and Sangre absorbing trace gases (greenhouse gases ter rather than summer. The important de Cristo ranges). Coldest temperatures such as carbon dioxide). climatic boundary conditions that vary are in the north-central mountains along If our planet were a featureless sphere, with longitude include the distribution of the Colorado border. then its climate would depend only on oceans and continents, continental topog- Many of the world’s deserts are located the distribution of sunlight, and would raphy, and land surface cover. The within the latitude zone between 25° and therefore be the same at each point along climate of Los Angeles is considerably 35° in either hemisphere, owing to a a latitude circle. This is obviously not the moderated by its proximity to the Pacific global circulation system called the

Published by the New Mexico Bureau of Geology and Mineral Resources • A Division of New Mexico Tech

Current Climate Variability place during a PDO-positive period. “Average weather” can vary Teasing out the association between systematically from year to year decadal climate variability across the within a 30-year climate period. Southwest and these slow, multi-decadal Such interannual variability is oceanic cycles in the Pacific (and perhaps associated principally with the Atlantic Ocean as well) is a very changes in ocean temperatures active area of research. that modulate storm tracks and Climate Change moisture transport for entire New Mexico’s climate is constantly easons or years. Slow variations changing over longer time scales, too. in ocean temperature and Over the past several decades the currents, especially in the Pacific statewide average temperature has risen Ocean, are a major cause of rather steadily and quite rapidly. An wintertime interannual variability 11-year running average of temperature across North America. The El started upward around 1970, and every Niño cycle is the best known and year since 1992 has been warmer than best understood example of the “climatological average” value of oceanic short-term climate 53.1°F, with no cooling trend in sight. forcing. El Niño is an enormous On the other hand, the early years of the tongue of anomalously warm twentieth century, and the 1960s and Pacific Ocean surface water early 1970s, were generally somewhat extending along the equator Climatological distribution of annual average cooler than this average value. The figure surface air temperature across the Southwest. westward from the South on page 3 illustrates both the very signifi- American coast. The mirror-image cant character of the current warming Hadley Cell that generates a belt of cold phase is typically called La Niña. trend (which is observed across much of subsiding air (which tends to suppress The cycle is not periodic, but extreme the world, hence the strong suspicion clouds and precipitation) at these latitudes. warm and cold phases each tend to occur (Albuquerque is at a latitude of about 35° several years per decade, reaching maxi- N.) In addition to this global circulation, mum amplitude in the Northern New Mexico’s remoteness from oceanic Hemisphere winter season. El Niño pulls moisture sources acts to keep our climate the North Pacific atmospheric , dry. The lack of humidity has a and the storm track associated with it, particularly pronounced cooling effect on southward and eastward, so that more of nighttime temperatures, because heat the winter storms that usually pass to our stored in surface soil readily radiates away north generate precipitation over New to space during the night. Precipitation Mexico instead (as happened in early increases across the eastern half of the 1983, 1987, and 1992). La Niña has the state, where humid air from the Gulf of opposite effect, pushing the jet stream Mexico penetrates more often, especially northward and leaving New Mexico drier in springtime. than normal (as in 1971, 1974, and New Mexico receives moisture and 1989). precipitation from a variety of directions. Recent research suggests that longer In winter most of the precipitation is multi-decadal fluctuations in the North carried in by eastward-moving frontal Pacific Ocean also affect precipitation systems originating over the Pacific Ocean. across southwest North America, perhaps In an average winter most of these storms helping to explain long-term drought and track to our north, dumping more in wet spells across the Southwest. North Colorado than in New Mexico. Winter Pacific Ocean temperatures seem to vary snow pack at high elevations is particularly more slowly than tropical El Niño-related important for water resources statewide, anomalies. This Pacific Decadal Oscillation (or PDO) seems to modulate because snowmelt provides a very effective Average annual precipitation across New means for recharging ground water and the effects of El Niño, such that in its Mexico. The pronounced effects of topogra- filling reservoirs. However, the wettest negative phase the effects of La Niña are phy on local precipitation are clearly evident. season for most of New Mexico is summer, amplified and the effects of El Niño are The dry Colorado Plateau country in the when thunderstorms can produce spotty suppressed, whereas in the PDO’s northwestern corner of the state has high but locally heavy precipitation across the positive phase the opposite modulation mountains blocking it from oceanic moisture state. In summer, rainy periods are marked occurs. The PDO was in a negative phase sources in all directions. More than 36 inches during the 1950s (when persistent of precipitation per year falls on the high by humid low-level from the south, peaks in the Mogollon, Sangre de Cristo, and part of the so-called North American drought plagued New Mexico), then Jemez Mountains; not far away, the middle system. abruptly flipped in 1977 so that the wet Rio Grande valley receives less than 10 decades of the 1980s and 1990s took inches per year.

NEW MEXICO EARTH MATTERS 2 SUMMER 2004

the Estancia Basin east of the Manzano Mountains. Layers in lake bed sediment cores, called varves, contain pollen grains, magnetized minerals, and tiny fossils that can be analyzed to determine the temperature of the lake and how long ago the sediment layer was laid down. Painstaking field work and labora- tory analysis yield dated maps of the sequence of former lake levels. The wetter climate that once supported large lakes in this now-arid land also generated huge ground water reservoirs that now provide us with much of our water supply. Geochemical evidence suggests that much of the well water we Time series of annual temperature averaged across New Mexico from 1896–2003. Each now tap must have seeped into the data point is an average from October through the following September (to avoid split- ground during the last ice age. The ting winters in half). Red line shows annual data points; blue x’s show 10-year running implication is that we are rapidly average. Data and plotting routine are available online from the Western Regional “mining” ground water from aquifers Climate Center at www.wrcc.dri.edu. An 11-year running average of temperature start- ed upward around 1970, with no cooling trend in sight. that filled up thousands of years ago, and our extraction of this water vastly that the warming can be attributed to when the 23.5° tilt of Earth’s rotational exceeds the recharge taking place under worldwide increases in greenhouse axis becomes smaller, making seasons less current, more arid climatic conditions. gases), and the difficulty in making pronounced. As ice sheets grow, less sun- Thus much of the ground water in New confident predictions of future light is absorbed by Earth’s surface Mexico, like oil, is effectively a nonre- temperature changes based just on (because ice is very reflective), amplifying newable resource on human timescales. extrapolating current trends. Our cold conditions. Bubbles of air trapped in New Mexico has undergone some understanding of “natural” climatic ice cores show that atmospheric CO2 very significant shifts in climate during cycles and trends has been considerably concentration declined dramatically to the past 10,000 years or so since the last complicated by the fact that we now around 200 parts per million during the major ice sheet retreated. At the have the ability to influence climate last ice age, decreasing the greenhouse University of New Mexico Professor (however unwittingly), though there is effect and thereby depressing temperature Peter Fawcett and his students, drilling considerable debate regarding the still further. into lake bed sediments in the Sangre de degree to which we are influencing it. Although New Mexico itself was not Cristo range and in a dried-up former Because natural and man-made climate covered with ice 20,000 years ago, the cli- lake in northern Mexico, have shown changes are now occurring simultane- mate here was still much cooler than at that the Southwest was much wetter ously in unprecedented ways, we present. Large lake beds, now just dry several thousand years ago than it is cannot confidently extrapolate past basins, stand as distinct evidence for a today. They have also found evidence for variability into the future. So the only very different climate regime. Bruce small glaciers in parts of northern New way to understand (and predict) future Allen of the New Mexico Bureau of Mexico that currently are unglaciated. changes in climate is to improve our Geology and Mineral Resources has New evidence for decade-scale climate understanding of the fundamental pro- examined one of these areas in consider- variability during the past 1,000 years cesses that govern the climate system. able detail: Lake Estancia, in what is now has recently come to light from Although the current warming trend in climate is very significant, projected twenty-first century climate changes are still modest compared to changes that have occurred in the past. During the last ice age, which maximized some 15,000–20,000 years ago, abundant geological evidence indicates that huge ice sheets covered much of North America to the north of New Mexico. This event was merely the latest of a long series of ice age cycles that charac- terize climate during the last 2 million years. These ice age cycles are thought to be caused by wobbles in Earth’s orbit that make Northern Hemisphere summers cold, such as would happen Reconstructed precipitation in south-central New Mexico, A.D. 622–1994, derived from tree ring records obtained in the Magdalena, San Mateo, and Organ Mountains.

NEW MEXICO EARTH MATTERS 3 SUMMER 2004

examination of annual growth rings in year return period for such droughts that in climate forecasting is very limited. To ancient trees, a proxy indicator of climate is not currently explained by any known achieve a better forecasting capability that was developed at the University of changes in boundary conditions. will require more thorough understand- Arizona early in the twentieth century. Furthermore, the terrible 1950s drought ing of how and why climate has changed The sequence of good and bad growth does not appear to be extraordinary in in the past, and an improved database years in the trees is so distinct that it terms of either duration or severity—just for monitoring today’s climate. provides an excellent “fingerprint,” allow- another “normal” feature of southwestern Geologists, atmospheric scientists, and ing archaeologists and geologists to climate variability! The lessons for us are computer science experts are working determine when trees were cut or died, clear: The most recent few decades repre- together to make this happen. an invaluable source of precise dating for sent unusually wet conditions, and we many scientific studies. One of the need to anticipate future droughts at —David S. Gutzler major results of recent tree ring analysis least as severe as the 1950s episode. Fifty Department of Earth & Planetary Sciences is the discovery of southwestern “drought years later, it is quite possible that we are University of New Mexico cycles” on sub-century time scales. A experiencing the next such drought right [email protected] time series derived from a set of old trees now, and climate histories like the tree David Gutzler is a professor of across southern New Mexico is illustrated ring record suggest that our current meteorology and climatology at the at the bottom of page 3. The severe drought could easily persist for several University of New Mexico in Albuquerque. 1950s drought shows up very clearly as more years. His research is focused on interannual and the last major negative departure on this Climate variability and change exert decadal variability and predictability of graph, followed by very positive (wet) profound influences on agriculture, climate in the Southwest. conditions in the latter half of the twen- natural ecosystems, wildfires, tourism, Each issue of Earth Matters features an tieth century. There are abundant and water resources in our state. Our invited article on a subject of interest to historical records of the late nineteenth vulnerability to climatic anomalies has New Mexicans. These articles represent the century drought, which spanned the turn been highlighted during the past few author’s informed opinion on important of the twentieth century, corroborating years of drought. The prospect of skillful geoscience issues in New Mexico. The New the tree ring record of that event. climate forecasting, which was inconceiv- Mexico Bureau of Geology and Mineral The tree ring record shows that able just a few decades ago, could Resources is a non-regulatory agency. intermittent severe droughts have been a provide a useful management tool for recurring feature of New Mexico’s policymakers and the public to reduce —Ed. climate. There is an apparent 50–100 our vulnerability. However, current skill

Bureau Staff Involved in Climate-related Research Several members of our staff are current- water table in the Albuquerque Basin, oxygen and hydrogen in the ice as well as ly involved in research directly related to Marshall is hoping to be able to identify the measuring the composition of gas changing climates. Bruce Allen in our changes in surface temperature over the bubbles trapped in the ice. These data Albuquerque office has worked in the past 100–200 years. can provide information about local cli- Estancia Basin for some years, focusing Geochemist Nelia Dunbar and matic variations over time and, on the Pleistocene lakes that occupied geochronologist Bill McIntosh spent six ultimately, will give us a window on this area when wetter conditions pre- weeks in Antarctica this past winter as global climate change. Dunbar and vailed. The geologic record from these part of a team of research scientists. McIntosh will focus on dating and basins—today occupied by much small- Their primary goal was the collection of chemically fingerprinting the suite of er, ephemeral lakes—stretches back climate-related ice samples at Mt. volcanic ashes, in order to provide time 45,000 years. A detailed examination of Moulton, in West Antarctica. The sum- lines for the climate information. this geologic record, obtained through mit crater of Mt. Moulton contains a Many of our staff are working on coring, provides a detailed look at cli- 600-meter-thick section of ice interbed- detailed geologic mapping in the matic fluctuations at the end of the last ded with at least 40 layers of volcanic ash Albuquerque Basin, unraveling the com- ice age. One long-term goal of this work from nearby Mount Berlin. Radioisotopic plex history of the Rio Grande, as well as is to provide us with a detailed regional dating of the ash indicates that the age of the sedimentary and tectonic history of climatic record for the past 50,000 years the Moulton ice ranges between at least the Rio Grande rift, for the past 20 mil- or so. 10,000 and 492,000 years. The site lion years. When completed, much of Geophysicist Marshall Reiter has for offers an unparalleled repository of this work will have implications for our some years been working on highly sen- ancient West Antarctic snow and trapped understanding of the climatic history of sitive well logs that measure ground air, which can be used to investigate the region, as well. water temperature as a function of West Antarctic climate over the last Details of this research and the ongo- depth. His work in the Albuquerque 500,000 years. Several aspects of this ing research of our other staff persons are Basin has been concerned primarily with unique climatic record will be investigat- available on individual staff Web pages discerning ground water flow patterns; ed by collaborative researchers at on our Web site at geoinfo.nmt.edu. these logs can offer some insight into cli- Pennsylvania State University and the mate change, as well. Logging University of Colorado, including ana- –L. Greer Price temperatures in the subsurface above the lyzing the isotopic composition of

NEW MEXICO EARTH MATTERS 4 SUMMER 2004 BUREAU NEWS This year’s annual teacher’s workshop, University of Texas in Austin. A number Rockin’ Around New Mexico, was held of bureau staff assisted with the training in Albuquerque in July. Forty-three exercise. teachers from all over the state attended. The three-day workshop included field We are soliciting nominations for the trips to Madrid, the Cunningham mine next New Mexico Earth Science in the Ortiz Mountains, the Rio Grande Achievement Awards, to be presented in cement plant, the Sandia Crest, and the January 2005. This annual award is co- Albuquerque volcanoes. This year’s work- sponsored by the bureau and New shop was led by Bill Chavez of New Mexico’s Energy, Minerals and Natural Mexico Tech and David Love from the Resources Department in Santa Fe. It is bureau, with help from other bureau presented annually to honor individuals who have made outstanding contribu- Volume 4, Number 2 staff. Special thanks to Larry Crumpler Published twice annually by the and Jayne Aubele from the New Mexico tions to advancing or facilitating the role NEW MEXICO BUREAU OF GEOLOGY Museum of Natural History and Science. of geoscience in areas of education, AND MINERAL RESOURCES This year’s sponsors included the New research, public service, and public policy Peter A. Scholle Mexico Department of Public Safety in New Mexico. Nominations for next Director and State Geologist year’s award are solicited from at large a division of /Office of Emergency Management, and NEW MEXICO INSTITUTE OF the New Mexico Mining and may be made at any time between MINING AND TECHNOLOGY Association/New Mexico Minerals now and January 1, 2005. Names should Daniel H. López Foundation. Next year’s Rockin’ will be be submitted directly to Peter Scholle at President the bureau ([email protected]). Last 801 Leroy Place held in Ruidoso. For more information, Socorro, New Mexico 87801-4796 contact Susie Welch at [email protected]. year’s awards went to Representative Joe (505) 835-5420 Stell of Carlsbad, for outstanding contri- Albuquerque Office This July the bureau participated in the butions advancing the role of earth 2808 Central SE Albuquerque training of sixteen NASA astronauts in science in areas of public service and New Mexico 87106 the Taos region. These days, with a public policy in New Mexico, and to Dr. (505) 366-2530 renewed interest in Mars, astronauts are John W. Shomaker of Albuquerque, for Visit our main Web site geoinfo.nmt.edu training in a variety of planetary explo- outstanding contributions advancing the ration techniques, including photo- role of earth science in areas of applied Board of Regents interpretation of landforms, rock and soil Ex Officio science and education in New Mexico. Bill Richardson sampling, and geophysical techniques. Governor of New Mexico Michael Timmons joined our staff in May The Taos region has long served as an Veronica C. Garcia extraterrestrial analog because of the sim- 2004 as manager of the bureau’s geologic Secretary of Education ilarity between the deeply canyoned Taos mapping program. He will be working Appointed volcanic plateau and the lunar surface. closely with our STATEMAP mappers and Jerry A. Armijo The project was organized by Paul Bauer with other staff on a variety of geologic President on our staff, in conjunction with Drs. mapping projects. Mike recently complet- 2003–2009, Socorro Patricia Dickerson and Bill Muehlberger, ed his Ph.D. at the University of New Richard N. Carpenter Mexico in Albuquerque. Secretary/Treasurer NASA contractors affiliated with the 2003–2009, Sante Fe Ann Murphy Daily OUR MISSION 1999–2004, Santa Fe The New Mexico Bureau of Geology • CREATE accurate, up-to-date (digital Sidney M. Gutierrez 2001–2007, Albuquerque and Mineral Resources, established by and GIS-based) maps of the state’s Isaiah K. Storey legislation in 1927, is a service and geology and resource potential. 2003–2005, Socorro research division of the New Mexico • PROVIDE timely information on Institute of Mining and Technology. Editors potential geologic hazards, including It acts as the geological survey of New L. Greer Price earthquakes, volcanic events, soils- Jane C. Love Mexico with these main goals: and subsidence-related problems, Layout • CONDUCT research and interact with and flooding. Thomas Kaus state and federal agencies and indus- • ACT as a repository for cores, well Graphics try to facilitate prudent exploitation Leo Gabaldon cuttings, and a wide variety of of the state’s geological resources. Thomas Kaus geological data. Provide convenient Earth Matters is a free publication. For • DISTRIBUTE accurate information to physical and internet access for subscription information please call scientists, decision makers, and the New Mexicans to such resources. (505) 835-5410, or e-mail us at New Mexico public regarding the [email protected] • PROVIDE public education and out- state’s geologic infrastructure, mineral Cover photo of Ship Rock, New Mexico by reach through college teaching and and energy resources, and geohydrol- Paul G. Logsdon advising, the Mineral Museum, and ogy (including water quantity and copyright © Marcia L. Logsdon. teacher- and student-training programs. quality). Reproduced with permission.

NEW MEXICO EARTH MATTERS 5 SUMMER 2004

NEW PUBLICATIONS

Publications catalog The Geology of New 2004–2005 Mexico—A Geologic History, 40 pp. Free edited by Greg H. Mack and This 40-page booklet offers a com- Katherine A. Giles, 2004, 474 pp., prehensive look at the variety of over 300 photos and illustrations, technical and popular publications color throughout. New Mexico available, including books, maps, Geological Society Special databases, and free publications. Publication 11. ISBN 1-58546- This is the first printed publica- 010-9 Hardcover $45.00 plus tions catalog issued in nearly 5 shipping and handling. Price for years. Special attention is given to student members $29.25 the bureau's most recently released This volume is the first of two and forthcoming publications; books on the geologic history and the economic geology of New however, all of the bureau's more than 400 in-print titles are Mexico. The books celebrate the society's 50th anniversary in listed (exclusive of open-file reports). A complete listing of 1999 and honor the many field geologists of the early and bureau publications, including open-file reports, is available on middle twentieth century whose geologic maps and comple- our Web site at geoinfo.nmt.edu mentary stratigraphic studies laid the foundation for our present understanding of the geologic history of New Mexico. For more information about these and other bureau publica- tions: visit our Web site at geoinfo.nmt.edu; write or visit our Nineteen chapters on major depositional and tectonic events Publications Office on the campus of New Mexico Tech, 801 are organized chronologically. Two final chapters on paleo- Leroy Place, Socorro, New Mexico 87801; call (505) 835- magnetism and the geophysical constraints on crustal structure 5410 or (505) 835-5490; or e-mail us at recognize the important role of geophysics in interpreting [email protected]. Payment (check or money order payable Earth history. The authors are either currently working on the to NMBGMR) must be enclosed with mailed orders. Telephone rocks in their chapter or are able to provide current informa- orders may be paid with VISA, Discover, American Express, or tion on rock types, age and correlation, and MasterCard. paleogeographic/paleotectonic interpretations.

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NEW MEXICO EARTH MATTERS 6 SUMMER 2004