AGW Observer

Observations of anthropogenic global warming

New research – hydrosphere (August 3, 2016)

Posted by Ari Jokimäki on August 3, 2016

Some of the latest papers on hydrosphere (oceans, lakes, ponds, rivers, streams, etc.) are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.

Highlights

Comparison of Global Precipitation Estimates across a Range of Temporal and Spatial Scales (Gehne et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0618.1

Abstract: Characteristics of precipitation estimates for rate and amount from three global High-resolution precipitation products (HRPPs), four global Climate Data Records (CDRs), and four reanalyses are compared. All data sets considered have at least daily temporal resolution. Estimates of global precipitation differ widely from one product to the next, with some differences likely due to differing goals in producing the estimates. HRPPs are intended to produce the best snapshot of the precipitation estimate locally. CDRs of precipitation emphasize homogeneity over instantaneous accuracy. Precipitation estimates from global reanalyses are dynamically consistent with the large scale circulation but tend to compare poorly to rain gauge estimates since they are forecast by the reanalysis system and precipitation is not assimilated. Regional differences among the estimates in the means and variances are as large as the means and variances, respectively. Even with similar monthly totals, precipitation rates vary significantly among the estimates. Temporal correlations among data sets are large at annual and daily time scales, suggesting that compensating bias errors at annual and random errors at daily time scales dominate the differences. However, the signal to noise ratio at intermediate (monthly) time scales can be large enough to result in high correlations overall. It is shown that differences on annual time scales and continental regions are around 0.8mm/d, which corresponds to 23W m−2. These wide variations in the estimates, even for global averages, highlight the need for better constrained precipitation products in the future.

Stable reconstruction of Arctic sea level for the 1950–2010 period (Svendsen et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JC011685/abstract

Abstract: Reconstruction of historical Arctic sea level is generally difficult due to the limited coverage and quality of both tide gauge and altimetry data in the area. Here a strategy to achieve a stable and plausible reconstruction of Arctic sea level from 1950 to today is presented. This work is based on the combination of tide gauge records and a new 20-year reprocessed satellite altimetry derived sea level pattern. Hence the study is limited to the area covered by satellite altimetry (68ºN and 82ºN). It is found that timestep cumulative reconstruction as suggested by Church and White (2000) may yield widely variable results and is difficult to stabilize due to the many gaps in both tide gauge and satellite data. A more robust sea level reconstruction approach is to use datum adjustment of the tide gauges in combination with satellite altimetry, as described by (Ray and Douglas, 2011). In this approach, a datum-fit of each tide gauges is used and the method takes into account the entirety of each tide gauge record. This makes the Arctic sea level reconstruction much less prone to drifting.

From our reconstruction, we found that the Arctic mean sea level trend is around 1.5 mm +/- 0.3 mm/y for the period 1950 to 2010, between 68ºN and 82ºN. This value is in good agreement with the global mean trend of 1.8 +/- 0.3 mm/y over the same period as found by Church and White (2004).

Lake Vanda: A sentinel for climate change in the McMurdo Sound Region of Antarctica (Castendyk et al. 2016) http://www.sciencedirect.com/science/article/pii/S092181811530014X

Abstract: Lake Vanda is a perennially ice-covered, meromictic, endorheic lake located in the McMurdo Dry Valleys of Antarctica, and an exceptional sentinel of climate change within the region. Lake levels rose 15 m over the past 68 years in response to climate-driven variability in ice-cover sublimation, meltwater production, and annual discharge of the Onyx River, the main source of water to the lake. Evidence from a new bathymetric map and water balance model combined with annual growth laminations in benthic mats suggest that the most recent filling trend began abruptly 80 years ago, in the early 1930s. This change increased lake volume by > 50%, triggered the formation of a new, upper, thermohaline convection cell, and cooled the lower convection cell cooled by at least 2 °C and the bottom-most waters by at > 4 °C. Additionally, the depth of the deep chlorophyll a maximum rose by > 2 m, and deep-growing benthic algal mats declined while shallow benthic mats colonized freshly inundated areas. We attribute changes in hydrology to regional variations in air flow related to the strength and position of the Amundsen Sea Low (ASL) pressure system which have increased the frequency of down-valley, föhn winds associated with surface air temperature warming in the McMurdo Dry Valleys. The ASL has also been implicated in the recent warming of the Antarctic Peninsula, and provides a common link for climate-related change on opposite sides of the continent. If this trend persists, Lake Vanda should continue to rise and cool over the next 200 years until a new equilibrium lake level is achieved. Most likely, future lake rise will lead to isothermal conditions not conducive to thermohaline convection, resulting in a drastically different physical, biogeochemical, and biological structure than observed today.

Ocean acidification in the subpolar North Atlantic: rates and mechanisms controlling pH changes (García-Ibáñez et al. 2016) http://www.biogeosciences.net/13/3701/2016/

Abstract: Repeated hydrographic sections provide critically needed data on and understanding of changes in basin-wide ocean CO2 chemistry over multi-decadal timescales. Here, high-quality measurements collected at twelve cruises carried out along the same track between 1991 and 2015 have been used to determine long-term changes in ocean CO2 chemistry and ocean acidification in the Irminger and Iceland basins of the North Atlantic Ocean. Trends were determined for each of the main water masses present and are discussed in the context of the basin-wide circulation. The pH has decreased in all water masses of the Irminger and Iceland basins over the past 25 years with the greatest changes in surface and intermediate waters (between −0.0010 ± 0.0001 and −0.0018 ± 0.0001 pH units yr-1). In order to disentangle the drivers of the pH changes, we decomposed the trends into their principal drivers: changes in temperature, salinity, total alkalinity (AT) and total dissolved inorganic carbon (both its natural and anthropogenic components). The increase in anthropogenic CO2 (Cant) was identified as the main agent of the pH decline, partially offset by AT increases. The acidification of intermediate waters caused by Cant uptake has been reinforced by the aging of the water masses over the period of our analysis. The pH decrease of the deep overflow waters in the Irminger basin was similar to that observed in the upper ocean and was mainly linked to the Cant increase, thus reflecting the recent contact of these deep waters with the atmosphere.

Uncertainty in the Himalayan energy–water nexus: estimating regional exposure to glacial lake outburst floods (Schwanghart et al. 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/7/074005/meta

Abstract: Himalayan water resources attract a rapidly growing number of hydroelectric power projects (HPP) to satisfy Asia’s soaring energy demands. Yet HPP operating or planned in steep, glacier-fed mountain rivers face hazards of glacial lake outburst floods (GLOFs) that can damage hydropower infrastructure, alter water and sediment yields, and compromise livelihoods downstream. Detailed appraisals of such GLOF hazards are limited to case studies, however, and a more comprehensive, systematic analysis remains elusive. To this end we estimate the regional exposure of 257 Himalayan HPP to GLOFs, using a flood-wave propagation model fed by Monte Carlo-derived outburst volumes of >2300 glacial lakes. We interpret the spread of thus modeled peak discharges as a predictive uncertainty that arises mainly from outburst volumes and dam-breach rates that are difficult to assess before dams fail. With 66% of sampled HPP are on potential GLOF tracks, up to one third of these HPP could experience GLOF discharges well above local design floods, as hydropower development continues to seek higher sites closer to glacial lakes. We compute that this systematic push of HPP into headwaters effectively doubles the uncertainty about GLOF peak discharge in these locations. Peak discharges farther downstream, in contrast, are easier to predict because GLOF waves attenuate rapidly. Considering this systematic pattern of regional GLOF exposure might aid the site selection of future Himalayan HPP. Our method can augment, and help to regularly update, current hazard assessments, given that global warming is likely changing the number and size of Himalayan meltwater lakes.

Other papers

Temporal and spatial variability of rainfall over Greece (Markonis et al. 2016) http://rd.springer.com/article/10.1007%2Fs00704-016-1878-7

The marine hydrological cycle: the Ocean’s floods and droughts (Gordon, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070279/abstract

The Contribution of Glacial Isostatic Adjustment to Projections of Sea Level Change Along the Atlantic and Gulf Coasts of North America (Love et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016EF000363/abstract

Modeled ecohydrological responses to climate change at seven small watersheds in the northeastern U.S (Pourmokhtarian et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13444/abstract

Data-model comparison of temporal variability in long-term time series of large-scale soil moisture (Verrot & Destouni, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JD025209/abstract

February drying in southeast Brazil and the Australian monsoon: Global mechanism for a regional rainfall feature (Kelly & Mapes, 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0838.1

Monotonic trends in spatio-temporal distribution and concentration of monsoon precipitation (1901–2002), West Bengal, India (Chatterjee et al. 2016) http://www.sciencedirect.com/science/article/pii/S0169809516301880

The Curious Nature of the Hemispheric Symmetry of the Earth’s Water and Energy Balances (Stephens et al. 2016) http://rd.springer.com/article/10.1007%2Fs40641-016-0043-9

Aragonite saturation states and pH in western Norwegian fjords: seasonal cycles and controlling factors, 2005–2009 (Omar et al. 2016) http://www.ocean-sci.net/12/937/2016/

Elevation change and the vulnerability of Rhode Island (USA) salt marshes to sea-level rise (Raposa et al. 2016) http://link.springer.com/article/10.1007%2Fs10113-016-1020-5

Precipitation sensitivity to warming estimated from long island records (Polson et al. 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/7/074024/meta

Stomatal response to humidity and CO2 implicated in recent decline in U.S. evaporation (Rigden & Salvucci, 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13439/abstract

International energy trade impacts on water resource crises: an embodied water flows perspective (Zhang et al. 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/7/074023/meta

Statistical analyses of potential evapotranspiration changes over the period 1930–2012 in the Nile River riparian countries (Onyutha, 2016) http://www.sciencedirect.com/science/article/pii/S0168192316302805

The influence from the shrinking cryosphere and strengthening evopotranspiration on hydrologic process in a cold basin, Qilian Mountains (Zongxing et al. 2016) http://www.sciencedirect.com/science/article/pii/S0921818115301508

Enhanced summer convective rainfall at Alpine high elevations in response to climate warming (Giorgi et al. 2016) http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2761.html

Assessing the impact of vertical land motion on 20th century global mean sea level estimates (Hamlington et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016JC011747/abstract

No observed effect of ocean acidification on nitrogen biogeochemistry in a summer Baltic Sea plankton community (Paul et al. 2016) http://www.biogeosciences.net/13/3901/2016/

Snowmelt Rate Dictates Streamflow (Barnhart et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069690/abstract

Impacts of open-ocean deep convection in the Weddell Sea on coastal and bottom water temperature (Wang et al. 2016) http://link.springer.com/article/10.1007%2Fs00382-016-3244-y

Intensification of upwelling along Oman coast in a Warming Scenario (Praveen et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069638/abstract

Ocean acidification affects marine chemical communication by changing structure and function of peptide signalling molecules (Roggatz et al. 2016) http://onlinelibrary.wiley.com/doi/10.1111/gcb.13354/abstract

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