Unusual Warming Research Articles

Where is El Niño?

I enjoyed George Philander's note, “Who is El Niño?,” (Eos, March 31, 1998, p. 170) and his effort to rationalize the Nino nomenclature. There is a further complication that he does not mention—the widespread labeling of El Niño as any unusual warming far from the equator, whether or not it is linked to the tropical event. This leads to considerable confusion, since the timings and intensities of these occurrences may be very different. For example, El Niño of 1972–1973 was a major event in the tropics that was associated with the collapse of the Peruvian anchoveta fishery, and yet significant sea‐surface temperature anomalies were barely detectable north of southern California. No one on the Washington coast would have called this El Niño. On the other hand, the minor tropical event of 1976–1977 was associated with the regime shift in the eastern North Pacificsemi; unusual surface warming as far north as the Bering Sea persisted into the early 1980s. Should both the 10‐month tropical event and the 5‐year subarctic event be called El Niño? The current frenzy over the 1997–1998 event, where subarctic warming was contemporaneous with equatorial developments, demonstrates the need to regularize the terminology.

El Niño in the 1990s

The evolution of the unusual warming events of the first half of the 1990s is discussed based on the National Center for Environmental Prediction ocean re‐analysis data, covering 1980–1995. The warmings occurring in 1991–1992, 1993, and 1994 are viewed as individual episodes, rather than as one long El Niño. It is shown that the warm episodes of the 1990s differ from previous El Niños in two important ways. First, subsurface anomalies are more strongly coupled to the mixed layer across the equatorial Pacific in the 1990s than in earlier years. Second, a persistent warm SST anomaly in the central Pacific has been instrumental in initiating warm events. Both of these factors interfere with the dominant mode of variability in the tropical Pacific air‐sea system, namely the delayed oscillator mechanism. We postulate that the low skill of dynamical atmosphere‐ocean models in predicting the recent warmings is related to a weakened delayed oscillator mechanism.

Midwinter weight gain of excised white spruce branchlets at the northern tree line

A net weight gain was recorded during midwinter abrasion experiments with 3-year-old branchlets excised from tree-line white spruce (Piceaglauca (Moench) Voss). Subsequent experimentation with 96 two-year-old branchlets, including 6 controls, confirmed an average weight gain of approximately 8% even though there was considerable needle loss from abrasion by wind-driven snow particles. A statistically significant pattern of weight gain was evident, with the largest branchlets, which had the lowest surface area to volume ratio, showing the least gain. A similar pattern in weight loss during thawing and drying of some of the branchlets indicates that the weight gain is apparently the result of rehydration during an unusual winter warming, when the ambient temperature exceeded −11 °C.

Heat flow measurements under some lakes in the Superior Province of the Canadian Shield: Discussion

In their recent paper Allis and Garland (1979) have attempted to make use of dimictic lakes for heat flow measurements. While recognizing that to allow for the effects of temperature changes at lake bottom it is necessary to apply large corrections to the temperatures and temperature gradients in the sediments, the form of the correction they have applied may not be sufficiently accurate to give reliable results. They show, in their Fig. 2, a temperature-time function for the bottoms of lakes which is essentially a square wave, with sudden temperature changes at 6 month intervals, on which is superimposed either a longer period change or an aperiodic change, and use a 30 term Fourier series to approximate the function. There are two problems with this approach which may lead to serious error in the estimate of the correction required. Firstly, since only 18 months of records are shown it is assumed that only 18 months of data are incorporated in the Fourier series, which implies that the longest term component has a period of less than 18 months; secondly, such a procedure implies a continuous temperature-time function for each term, whatever its period, which conflicts with their statement that the 2 K temperature rise in May 1976 was due to a period of unusual warmth and, therefore, should presumably be treated as a unique event. In what follows I shall, for the sake of simplicity, assume sediment surface (i.e., lake bottom) temperature disturbances of unit amplitude. Figure 1, which is included as a form of baseline against which to compare other sets of curves, illustrates the disturbances to the temperature gradient due to an annual sinusoidal variation of V = Vo cos (2n tlP), where P (= 1 year) is the period, at the surface of sediments of diffusivity = 0.17 mm2/s; the numbers on the curves represent the time, in months, at which the gradients are measured using the time at which V = V, as the reference zero time. Sinusoidal changes of different period and amplitude would have a similar symmetrical appearance but would, of course, be of different amplitude at different depths. For the basic square wave function shown by Allis and Garland, the disturbance to gradients in the lake sediment should be computed on the basis of repetitive step functions (Beck 1977) and it is easy to show that even with equal amplitude steps the resultant computation based upon data for only 1 year will be very different from that based upon data for 2 to several years. This is illustrated in Fig. 2 using a sediment diffusivity of 0.17 mm2/s. Figure 2a shows curves for corrections to the temperature gradient due to unit change of temperature at t = 0 followed by a similar change of opposite sign at t = 6 months; the number on a curve represents the number of months (1 month = 30 days) that have passed, after the initial disturbance, before a measurement is made. This approach can be used for

Archives In Canada

IS a very great delight for me to be able to attend this meetof American archivists and historians and I esteem it a special honour to represent Canada, in so far as the gathering is international in character. Canadians have never been able to regard the Americans as foreigners. We usually refer to them as our cousins. This easy relationship enables us to offer them greetings of special affection, criticisms of unusual warmth, or other exchanges of particular intimacy. Since Canada has in part, a strong Latin tradition we have also a kindly neighborly interest in Mexico and the other great states of the south. We have met here to discuss problems which have a common or universal significance as well as national and local importance. You have asked me to make my contribution by describing briefly the Archives situation in Canada. Although Archives to most people represent an obscure and remote institution which is narrowly specialized in its organization and serves a relatively few people, actually they reflect faithfully the life, spirit and history of a people. The dynamic which creates archives and maintains their vitality springs from three primary sources: a sense of tidiness, a sense of tradition and a sense of crisis.

A WARM WINTER (1920–21) FOLLOWED BY A WARM SUMMER

Abstract SYNOPSIS This paper is in the nature of a preliminary report on the period of abnormal warmth in the United States and Canada which began in September, 1920, and ended with July, 1921. The location of the areas of maximum positive departure of temperature from the normal from month to month are traced and three periods of abnormal warmth are distinguished. The end of each period of abnormal warmth is evidently marked by a brief and ineffective reaction to lower temperature which soon gave way to a second and third period of unusual warmth. The meteorological conditions as to pressure, over the United States and the adjacent oceans, the prevailing winds, the number of areas of low pressure (cyclones) plotted during the 11 months are briefly discussed and the most important conclusion reached will be found in the closing paragraph.

Noteworthy Weather Records

AN interesting article on “The High Temperature of the Twelve Months May, 1911, to April, 1912,” is published in Symons's Meteorological Magazine for May. Dr. Mill points out that for the first time in the Camden Square (N.W. London) record there has been a run of twelve consecutive months in each of which the mean temperature has been above the average of fifty years. In 1911 the month of April was the only one below the average. The mean temperature for the twelve months above quoted was 53.1°, or 3.1° above the average. The nearest approach to this figure for any twelve successive months in the past fifty-four years was 52.8° for the period March, 1868, to February, 1869. The most severe frosts of last winter occurred in the first week of February, but the unusual warmth of the latter part of the month raised the mean temperature 3.6° above the average. March was also very remarkable for its warmth, both the mean temperature, 46.5°, and the mean shade minimum, 40.5°, being the highest on record for March. There were no frosts in the screen.