Ocean Heat and Carbon Uptake in Transient Climate Change: Identifying Model Uncertainty

Global warming on decadal and centennial timescales is mediated and ameliorated by the oceansequestering heat and carbon into its interior. Transient climate change is a function of the efficiency by whichanthropogenic heat and carbon are transported away from the surface into the ocean interior (Hansen et al. 1985).Gregory and Mitchell (1997) and Raper et al. (2002) were the first to identify the importance of the ocean heat uptakeefficiency in transient climate change. Observational estimates (Schwartz 2012) and inferences from coupledatmosphere-ocean general circulation models (AOGCMs; Gregory and Forster 2008; Marotzke et al. 2015), suggest thatocean heat uptake efficiency on decadal timescales lies in the range 0.5-1.5 W/sq m/K and is thus comparable to theclimate feedback parameter (Murphy et al. 2009). Moreover, the ocean not only plays a key role in setting the timing ofwarming but also its regional patterns (Marshall et al. 2014), which is crucial to our understanding of regional climate,carbon and heat uptake, and sea-level change. This short communication is based on a presentation given by A.Romanou at a recent workshop, Oceans Carbon and Heat Uptake: Uncertainties and Metrics, co-hosted by US CLIVARand OCB. As briefly reviewed below, we have incomplete but growing knowledge of how ocean models used in climatechange projections sequester heat and carbon into the interior. To understand and thence reduce errors and biases inthe ocean component of coupled models, as well as elucidate the key mechanisms at work, in the final section we outlinea proposed model intercomparison project named FAFMIP. In FAFMIP, coupled integrations would be carried out withprescribed overrides of wind stress and freshwater and heat fluxes acting at the sea surface

Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux Variability on Daily Through Decadal Time Scales

We analyze daily wintertime cyclone variability in the central and eastern Mediterranean during 1958-2001, and identify four distinct cyclone states, corresponding to the presence or absence of cyclones in each basin. Each cyclone state is associated with wind flows that induce characteristic patterns of cooling via turbulent (sensible and latent) heat fluxes in the eastern Mediterranean basin and Aegean Sea. The relative frequency of occurrence of each state determines the heat loss from the Aegean Sea during that winter, with largest heat losses occurring when there is a storm in the eastern but not central Mediterranean (eNOTc), and the smallest occurring when there is a storm in the central but not eastern Mediterranean (cNOTe). Time series of daily cyclone states for each winter allow us to infer Aegean Sea cooling for winters prior to 1985, the earliest year for which we have daily heat flux observations. We show that cyclone states conducive to Aegean Sea convection occurred in 1991/1992 and 1992/1993, the winters during which deep water formation was observed in the Aegean Sea, and also during the mid-1970s and the winters of 1963/1964 and 1968/1969. We find that the eNOTc cyclone state is anticorrelated with the North Atlantic Oscillation (NAO) prior to 1977/1978. After 1977/1978, the cNOTe state is anticorrelated with both the NAO and the North Caspian Pattern (NCP), showing that the area of influence of large scale atmospheric teleconnections on regional cyclone activity shifted from the eastern to the central Mediterranean during the late 1970s. A trend toward more frequent occurrence of the positive phase of the NAO produced less frequent cNOTe states since the late 1970s, increasing the number of days with strong cooling of the Aegean Sea surface waters

Natural ocean carbon cycle sensitivity to parameterizations of the recycling in a climate model

Sensitivities of the oceanic biological pump within the GISS (Goddard Institute for Space Studies ) climate modeling system are explored here. Results are presented from twin control simulations of the air–sea CO₂ gas exchange using two different ocean models coupled to the same atmosphere. The two ocean models (Russell ocean model and Hybrid Coordinate Ocean Model, HYCOM) use different vertical coordinate systems, and therefore different representations of column physics. Both variants of the GISS climate model are coupled to the same ocean biogeochemistry module (the NASA Ocean Biogeochemistry Model, NOBM), which computes prognostic distributions for biotic and abiotic fields that influence the air–sea flux of CO₂ and the deep ocean carbon transport and storage. In particular, the model differences due to remineralization rate changes are compared to differences attributed to physical processes modeled differently in the two ocean models such as ventilation, mixing, eddy stirring and vertical advection. GISSEH(GISSER) is found to underestimate mixed layer depth compared to observations by about 55% (10%) in the Southern Ocean and overestimate it by about 17% (underestimate by 2%) in the northern high latitudes. Everywhere else in the global ocean, the two models underestimate the surface mixing by about 12–34%, which prevents deep nutrients from reaching the surface and promoting primary production there. Consequently, carbon export is reduced because of reduced production at the surface. Furthermore, carbon export is particularly sensitive to remineralization rate changes in the frontal regions of the subtropical gyres and at the Equator and this sensitivity in the model is much higher than the sensitivity to physical processes such as vertical mixing, vertical advection and mesoscale eddy transport. At depth, GISSER, which has a significant warm bias, remineralizes nutrients and carbon faster thereby producing more nutrients and carbon at depth, which eventually resurfaces with the global thermohaline circulation especially in the Southern Ocean. Because of the reduced primary production and carbon export in GISSEH compared to GISSER, the biological pump efficiency, i.e., the ratio of primary production and carbon export at 75 m, is half in the GISSEH of that in GISSER, The Southern Ocean emerges as a key region where the CO₂ flux is as sensitive to biological parameterizations as it is to physical parameterizations. The fidelity of ocean mixing in the Southern Ocean compared to observations is shown to be a good indicator of the magnitude of the biological pump efficiency regardless of physical model choice

The ocean’s role in the transient response of climate to abrupt greenhouse gas forcing

We study the role of the ocean in setting the patterns and timescale of the transient response of the climate to anthropogenic greenhouse gas forcing. A novel framework is set out which involves integration of an ocean-only model in which the anthropogenic temperature signal is forced from the surface by anomalous downwelling heat fluxes and damped at a rate controlled by a ‘climate feedback’ parameter. We observe a broad correspondence between the evolution of the anthropogenic temperature (T[subscript anthro]) in our simplified ocean-only model and that of coupled climate models perturbed by a quadrupling of CO[subscript 2]. This suggests that many of the mechanisms at work in fully coupled models are captured by our idealized ocean-only system. The framework allows us to probe the role of the ocean in delaying warming signals in the Southern Ocean and in the northern North Atlantic, and in amplifying the warming signal in the Arctic. By comparing active and passive temperature-like tracers we assess the degree to which changes in ocean circulation play a role in setting the distribution and evolution of T[subscript anthro]. The background ocean circulation strongly influences the large-scale patterns of ocean heat uptake and storage, such that T[subscript anthro] is governed by an advection/diffusion equation and weakly damped to the atmosphere at a rate set by climate feedbacks. Where warming is sufficiently small, for example in the Southern Ocean, changes in ocean circulation play a secondary role. In other regions, most noticeably in the North Atlantic, changes in ocean circulation induced by T[subscript anthro] are central in shaping the response.United States. National Aeronautics and Space Administration. Modeling, Analysis, and Prediction ProgramMassachusetts Institute of Technology. Joint Program on the Science & Policy of Global ChangeJames S. McDonnell Foundation (Postdoctoral Fellowship

Chapter 12: Sea Level Rise

Global mean sea level (GMSL) has risen by about 7-8 inches (about 16-21 cm) since 1900, with about 3 of those inches (about 7 cm) occurring since 1993. Human-caused climate change has made a substantial contribution to GMSL rise since 1900, contributing to a rate of rise that is greater than during any preceding century in at least 2,800 years. Relative to the year 2000, GMSL is very likely to rise by 0.3-0.6 feet (9-18 cm) by 2030, 0.5-1.2 feet (15-38 cm) by 2050, and 1.0-4.3 feet (30-130 cm) by 2100. Future pathways have little effect on projected GMSL rise in the first half of the century, but significantly affect projections for the second half of the century. Emerging science regarding Antarctic ice sheet stability suggests that, for high emission scenarios, a GMSL rise exceeding 8 feet (2.4 m) by 2100 is physically possible, although the probability of such an extreme outcome cannot currently be assessed. Regardless of pathway, it is extremely likely that GMSL rise will continue beyond 2100. Relative sea level (RSL) rise in this century will vary along U.S. coastlines due, in part, to changes in Earth's gravitational field and rotation from melting of land ice, changes in ocean circulation, and vertical land motion (very high confidence). For almost all future GMSL rise scenarios, RSL rise is likely to be greater than the global average in the U.S. Northeast and the western Gulf of Mexico. In intermediate and low GMSL rise scenarios, RSL rise is likely to be less than the global average in much of the Pacific Northwest and Alaska. For high GMSL rise scenarios, RSL rise is likely to be higher than the global average along all U.S. coastlines outside Alaska. Almost all U.S. coastlines experience more than global mean sea level rise in response to Antarctic ice loss, and thus would be particularly affected under extreme GMSL rise scenarios involving substantial Antarctic mass loss. As sea levels have risen, the number of tidal floods each year that cause minor impacts (also called "nuisance floods") have increased 5- to 10-fold since the 1960s in several U.S. coastal cities. Rates of increase are accelerating in over 25 Atlantic and Gulf Coast cities. Tidal flooding will continue increasing in depth, frequency, and extent this century. Assuming storm characteristics do not change, sea level rise will increase the frequency and extent of extreme flooding associated with coastal storms, such as hurricanes and nor'easters. A projected increase in the intensity of hurricanes in the North Atlantic could increase the probability of extreme flooding along most of the U.S. Atlantic and Gulf Coast states beyond what would be projected based solely on RSL rise. However, there is low confidence in the projected increase in frequency of intense Atlantic hurricanes, and the associated flood risk amplification and flood effects could be offset or amplified by such factors as changes in overall storm frequency or tracks

Глобализација и западна музичка историографија

Globalisation of musicology and music history aims to fuse the divisions created during Western music’s acme, and is referred to as “post-European historical thinking”. Therefore, “post” and “pre” European historical thinking have much in common. One aspect of this process of fragmentation was that music history was separated from theory and that Western Music Histories succeeded General Music Histories (a development described in some detail in the article). Connecting global music history with “post-European” historical thinking is one among numerous indications of Western awareness that European culture has reached some sort of a terminal phase. Concurrently, countries that have been developing by following Western Europe as a prototype, are leading today some past phase of Western development, which, with the ideas of cultural relativism prevailing, are not considered inferior.На основу садржаја уводне студије објављене у часопису Acta Musicologica (2014) и истраживачког пројекта Према глобалној историји музике, којим руководи оксфордски професор Рејнхард Стром, ауторка коментарише настојања западних музиколога да отворе нову еру глобалног музичког мишљења. Она бележи да је од ренесансе, па до врхунца западне музике у XIX веку, фрагментација музичког живота (композиција, извођаштво, образовање, градња инструмената, музичко издаваштво итд.) била заправо пут ка савршенству. Усавршавање у извођењу музичких дела, њиховом стварању и пласману на тржишту зависило је од уплива грађанства у главне културне токове. Један аспект тог процеса било је одвајање музичке историје од теорије музике и од чињенице да је историјски развој западне музике следио пут опште историје музике (то је у тексту детаљније приказано). Према мишљењу Герија Томлинсона, постепено је нарушавано некадашње јединство антропологије и историје (данас пак постоје тежње ка њиховом поновном уједињењу). Фрагментација широке дисциплине доноси могућност научничке перфекције, али и инфлацију професионалаца. У XX веку се дошло до таквих крајности да су у многим пољима дисциплине изнети неодговарајући закључци и постављени бесмислени циљеви. Глобализација тежи да превазиђе све границе. Повезивање глобалне музичке историје са „постевропским” историјским мишљењем један је од многобројних показатеља да на Западу постоји свест о томе да је европска култура достигла неку врсту своје завршне фазе. Но, земље којима је западна цивилизација била парадигма сопственог развоја следе раније фазе западне културе. Новина данашње манифестације овог феномена је начин на који је он суочен са самом западном историографијом. Под јаким утицајем културног релативизма, западни историчари који теже глобалној историји покушавају да из својих расуђивања усмерених ка култури искључе квалитативна поређења и идеју напретка. Будући да напредак није значајан за културу, историјско време се чини неважним, а историја поново дели са антропологијом задобијене одлике. Ови концепти су значајно утицали на етномузикологију у југоисточној Европи, у којој данас сарађују музичари и научници, превазилазећи границе међу нацијама и дисциплинама. Биће потребно да протекне одређено време да би се смисао нових прилика које је донео прелазак у постевропско доба схватио, као и да би се видело шта те прилике заиста доносе музикологији. За сада, видимо само оно што је изгубљено; још увек не спознајемо шта је добијено

Forcing and response in simulated 20th and 21st century surface energy and precipitation trends

A simple methodology is applied to a transient integration of the Met Office Hadley Centre Global Environmental Model version1 (UKMO-HadGEM1) fully coupled atmosphere-ocean general circulation model in order to separate forcing from climate response in simulated 20th century and future global mean surface energy and precipitation trends. Forcings include any fast responses that are caused by the forcing agent and that are independent of global temperature change. Results reveal that surface radiative forcing is dominated by shortwave forcing over the 20th and 21st centuries, which is strongly negative. However, when fast responses of surface turbulent heat fluxes are separated from climate feedbacks, and included in the forcing, net surface forcing becomes positive. The nonradiative forcings are the result of rapid surface and tropospheric adjustments and impact 20th century, as well as future, evaporation and precipitation trends. A comparison of energy balance changes in eight different climate models finds that all models exhibit a positive surface energy imbalance by the late 20th century. However, there is considerable disagreement in how this imbalance is partitioned between the longwave, shortwave, latent heat and sensible heat fluxes. In particular, all models show reductions in shortwave radiation absorbed at the surface by the late 20th century compared to the pre-industrial control state, but the spread of this reduction leads to differences in the sign of their latent heat flux changes and thus in the sign of their hydrological responses