Nas últimas décadas, particularmente desde a década de 1970, testemunhou-se um rápido recuo das geleiras em várias partes dos Andes tropicais. Uma tendência de aquecimento foi observada na região durante o mesmo período, com um hiato recente desde no início de 2010. No entanto, este hiato pode não ser o principal fator a influenciar as observações de aquecimento e recuo das geleiras em altitudes elevadas nos Andes tropicais. Com o surgimento de imagens de alta resolução espacial e espectral, e de modelos digitais de elevação (MDE) de alta resolução, agora é possível compreender as mudanças multitemporais das geleiras, o que era difícil de realizar utilizando as técnicas tradicionais e os dados de baixa resolução. Neste trabalho foram calculadas as variações da linha de neve das geleiras selecionadas ao longo dos Andes tropicais desde o início de 1980. A linha de neve máxima observada durante a estação seca (inverno austral) nos trópicos pode ser considerada como equivalente à linha de equilíbrio que separa a zona de acumulação da zona de ablação. A fim de reduzir o erro na estimativa da linha de neve foram consideradas somente as geleiras com declividades menores que 20o. Dependendo da região estudada e da presença de cobertura de nuvens, foram selecionadas imagens de várias fontes. As imagens da série Landsat (MSS, TM, ETM+ e OLI), EO1 OLI, ASTER e IRS LISS III foram usadas junto com MDE do ASTER GDEM-v2. Três bandas espectrais (TM5 - infravermelho médio, TM4- infravermelho próximo e TM2 - verde) foram utilizadas para calcular a linha de neve durante a estação seca, aplicando limiares adequados para TM4 e TM2. Os conjuntos de dados meteorológicos de várias fontes também foram analisados para observar as mudanças na precipitação, na temperatura e na umidade que influenciam os parâmetros glaciológicos como: o balanço de massa e a linha de equilíbrio. Geleiras representativas nos trópicos internos e trópicos externos foram consideradas separadamente dentro de um novo quadro, que foi baseado na precipitação, umidade e condições de temperatura ao longo da América do Sul. Neste âmbito, os Andes tropicais são classificados em trópicos internos, trópicos externos úmidos do norte, trópicos externos úmidos do sul e os trópicos externos secos. O Vulcão Cotopaxi no Equador (trópicos internos), o Nevado Caullaraju-Pastoruri que é uma geleira na Cordilheira Branca no Peru (trópicos externos úmidos do norte), o Nevado Cololo na Cordilheira Apolobamba na Bolívia (trópicos externos úmidos do sul), o Nevado Coropuna na Cordilheira Ampato no Peru e o Nevado Sajama na Cordilheira Ocidental da Bolívia (trópicos externos secos) são as geleiras representativas de cada grupo consideradas neste estudo. As geleiras tropicais nos trópicos internos, especialmente as situadas perto da Zona de Convergência Intertropicais (ZCIT), são mais vulneráveis a aumentos na temperatura e menos sensíveis a variações na precipitação. Em contraste, as geleiras nos trópicos externos respondem à variabilidade de precipitação muito rapidamente em comparação com a variação de temperatura, particularmente quando se deslocam para as regiões subtropicais. A dependência do balanço de massa sobre as características de sublimação também aumenta a partir dos trópicos internos para os trópicos externos. As condições de aquecimento, com maior umidade, tendem a aumentar a perda de massa por causa do derretimento em vez da sublimação. A elevação da umidade nos trópicos externos pode alterar as geleiras dominadas pela sublimação (nos trópicos externos e subtrópicos) e para as geleiras dominadas por derretimento. Observa-se que as geleiras próximas da ZCIT (trópicos internos e trópicosexternos úmidos do sul) estão recuando mais rapidamente como uma resposta ao aquecimento global, enquanto que as geleiras nos trópicos externos úmidos do norte e trópicos externos secos mostraram recuo relativamente mais lento. Possivelmente isso pode ser devido à ocorrência de fases frias do El Niño - Oscilação Sul (ENOS) conjuntamente com a Oscilação Decenal do Pacífico (ODP). As anomalias observadas nas variáveis meteorológicas seguem os padrões de ODP e as variações anuais de linha de neve seguem eventos de El Niño particularmente na fase ODP quente. No entanto, uma forte correlação entre as variações da linha de neve e dos fenômenos ENOS (e ODP) não está estabelecida. As geleiras do Equador mostram menos retração em resposta à tendência de aquecimento se comparadas às observações feitas por outros pesquisadores na Colômbia e na Venezuela, provavelmente devido à grande altitude das geleiras equatorianas. Em poucas palavras, as geleiras menores e em baixas altitudes nos trópicos internos e trópicos externos úmidos do sul estão desaparecendo mais rapidamente do que outras geleiras nos Andes tropicais. Também se observou neste estudo a existência de uma propriedade direcional no recuo das geleiras, o que não se observou em quaisquer outros estudos recentes. As geleiras nas cordilheiras leste do Peru e da Bolívia, que alimentam muitos rios nos lados leste das cordilheiras orientais, estão recuando do que aquelas geleiras situadas nas encostas ocidentais dos Andes tropicais. / Recent decades, particularly since the late 1970s, witnessed a rapid retreat of glaciers in many parts of the tropical Andes. A warming trend is observed in this region during the same period, with a recent hiatus since the early 2010s. However, this hiatus is observed to have not influenced the retreat of high elevation glaciers in the tropical Andes. Due to the emergence of high spatial and spectral resolution images and high quality digital elevation models (DEM), it is now possible to understand the multi-temporal glacier changes compared with the techniques that existed a few decades before. We calculated the snowline variations of selected glaciers along the tropical Andes since the early 1980s. The maximum snowline observed during the dry season (austral winter) in the tropics can be considered as nearly equivalent to the equilibrium line that separates the accumulation zone from the ablation zone. In order to reduce the error in the estimated snowline, glaciers with slopes < 20o only were considered in this research. Depending on the study region and the presence of cloud cover, images from multiple sources were selected. Landsat series (MSS, TM, ETM+, and OLI), EO1 OLI, ASTER, and IRS LISS III images were used along with digital elevation models (DEM) from ASTER GDEM-v2. Three wavebands (TM5 - Middle Infrared, TM4 - Near Infrared, and TM2 - Green) were used to calculate the dry season snowline, after applying suitable threshold values to TM4 and TM2. Meteorological datasets from multiple sources were also analysed to observe the changes in precipitation, temperature, and humidity that influence key glaciological parameters such as the mass balance and the equilibrium line. Representative glaciers in the inner and the outer tropical Andes were considered separately within a new framework, which is based on the precipitation, humidity, and temperature conditions along the South America. In this framework, tropical Andes are classified in to inner tropics, northern wet outer tropics, southern wet outer tropics, and dry outer tropics. Cotopaxi ice-covered volcano, Ecuador (inner tropics), Nevado Caullaraju-Pastoruri Glacier, Cordillera Blanca, Peru (northern wet outer tropics), Nevado Cololo, Cordillera Apolobamba, Bolivia (southern wet outer tropics), and Nevado Coropuna, Cordillera Ampato Peru and Nevado Sajama, Cordillera Occidental, Bolivia (dry outer tropics) are the representative glaciers in each group considered in this study. Inner tropical glaciers, particularly those situated near the January Intertropical Convergence Zone (ITCZ), are more vulnerable to increases in temperature and these glaciers are less sensitive to variations in precipitation. In contrast, outer tropical glaciers respond to precipitation variability very rapidly in comparison with the temperature variability, particularly when moving towards the subtropics. Mass balance dependency on sublimation characteristics also increases from the inner tropics to the outer tropics. Warming conditions with higher humidity tends to enhance mass loss due to melting rather than sublimation. Increased humidity observed in the outer tropics may change the sublimation dominated glaciers in the outer tropics and subtropics to melting dominated ones in the future. It is observed that the glaciers above and near the January ITCZ (inner tropics and southern wet outer tropics) are retreating faster as a response to global warming, whereas the glaciers in the northern wet outer tropics and dry outer tropics show relatively slower retreat. This can be possibly due to the occurrence of cold phases of El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) together. The observed anomalies in the meteorological variables slightly follow PDO patterns and the variations in annual snowlines follows El Niño events, particularly when in phase with warm PDO. However, a strong correlation between snowline variations and ENSO (and PDO) is not established. Mountain glaciers in Ecuador show less retreat in response to the warming trend compared with observations done by other researchers in Colombia and Venezuela, probably due to very high altitude of the Ecuadorean glaciers. In a nutshell, smaller glaciers at lower altitudes in the inner tropics and the southern wet outer tropics are disappearing faster than other glaciers in the tropical Andes. Another observation made in this study is the directional property of glacier retreat, which was not covered in any other recent studies. Those glaciers on the eastern cordilleras of Peru and Bolivia, which feed many rivers on the eastern sides of the eastern cordilleras, are retreating faster than those glaciers situated on the western sides.

We used long-term observations of grassland aboveground net plant production (ANPP, 19392016), growing seasonal advanced very-high-resolution radiometer remote sensing normalized difference vegetation index (NDVI) data (1982-2016), and simulations of actual evapotranspiration (1912-2016) to evaluate the impact of Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO) sea surface temperature (SST) anomalies on a semiarid grassland in northeastern Colorado. Because ANPP was well correlated (R-2 = 0.58) to cumulative April to July actual evapotranspiration (iAET) and cumulative growing season NDVI (iNDVI) was well correlated to iAET and ANPP (R-2 = 0.62 [quadratic model] and 0.59, respectively), we were able to quantify interactions between the long-duration (15-30 yr) PDO temperature cycles and annual-duration ENSO SST phases on ANPP. We found that during cold-phase PDOs, mean ANPP and iNDVI were lower, and the frequency of low ANPP years (drought years) was much higher, compared to warm-phase PDO years. In addition, ANPP, iNDVI, and iAET were highly variable during the cold-phase PDOs. When NINO-3 (ENSO index) values were negative, there was a higher frequency of droughts and lower frequency of wet years regardless of the PDO phase. PDO and NINO-3 anomalies reinforced each other resulting in a high frequency of above-normal iAET (52%) and low frequency of drought (20%) when both PDO and NINO-3 values were positive and the opposite pattern when both PDO and NINO-3 values were negative (24% frequency of above normal and 48% frequency of drought). Precipitation variability and subsequent ANPP dynamics in this grassland were dampened when PDO and NINO-3 SSTs had opposing signs. Thus, primary signatures of these SSTs in this semiarid grassland are (1) increased interannual variability in ANPP during cold-phase PDOs, (2) drought with low ANPP occurring in almost half of those years with negative values of PDO and NINO-3, and (3) high precipitation and ANPP common in years with positive PDO and NINO-3 values.

Noteworthy species endemic to the Galapagos Islands off Ecuador are two flightless birds, the Galapagos Penguin (Spheniscus mendiculus) and Flightless Cormorant (Phalacrocrax harrisi). Both adapted increased swimming ability at the cost of flight. This however has limited their ability to find richer feeding grounds in times of low resource availability, or to escape potential predators. Their population numbers, though small, were stable. Stress on this stability has increased since human arrival. Various invasive species from pets, farm animals and rats to even mosquito vectors of avian disease accompanied humans. . El Nino Southern Oscillation or ENSO cycles of warm waters in the Pacific Ocean south of the Equator cause drastic drops in food sources for all Galapagos seabirds. Serious ENSO events in 1983 and 1998 caused some species’ populations to drop by as much as 77%. Periodic less severe cycles may help explain how population recovery has not rebounded to earlier numbers. Reduced chick survival and adult fecundity seem to occur in concert with mild events. With available data and use of a modeling approach, this study focuses and explores their situations. Restoring population stability may include use of models, species monitoring, conservation and limiting invasive species. Usher matrices based on different climate conditions were produced using data combined from current and past census counts and weather. Models are used to compare available census data and test reliable predictors. Climate data from National Oceanic and Atmospheric Administration and the University of Florida provides for testing predictions of current and probable future climate change. Life histories of both species are regarded. Results suggest the current Cormorant population is still stable. The Penguin, however, faces a 20% probability of extinction in 100 years if current conditions remain. Extinction probability rises to 60% if climate change continues to worsen. Interventions such as captive breeding could be suitable for population recovery.

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