Rapid and highly variable warming of lake surface waters around the globe

In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade−1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors—from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade−1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade−1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.Peer reviewe

Constraining modern day silicon cycling in Lake Baikal

Constraining the continental silicon cycle is a key requirement in attempts to understand both nutrient fluxes to the ocean and linkages between silicon and carbon cycling over different timescales. Silicon isotope data of dissolved silica (δ30SiDSi) are presented here from Lake Baikal and its catchment in central Siberia. As well as being the world's oldest and voluminous lake, Lake Baikal lies within the seventh largest drainage basin in the world and exports significant amounts of freshwater into the Arctic Ocean. Data from river waters accounting for c. 92% of annual river inflow to the lake suggest no seasonal alteration or anthropogenic impact on river δ30SiDSi composition. The absence of a change in δ30SiDSi within the Selenga Delta, through which 62% of riverine flow passes, suggest a net balance between biogenic uptake and dissolution in this system. A key feature of this study is the use of δ30SiDSi to examine seasonal and spatial variations in DSi utilisation and export across the lake. Using an open system model against deep water δ30SiDSi values from the lake, we estimate that 20-24% of DSi entering Lake Baikal is exported into the sediment record. Whilst highlighting the impact that lakes may have upon the sequestration of continental DSi, mixed layer δ30SiDSi values from 2003 and 2013 show significant spatial variability in the magnitude of spring bloom nutrient utilisation with lower rates in the north relative to south basin

Holocene carbon dynamics at the forest – steppe ecotone of southern Siberia

The forest–steppe ecotone in southern Siberia is highly sensitive to climate change; global warming is expected to push the ecotone northwards, at the same time resulting in degradation of the underlying permafrost. To gain a deeper understanding of long-term forest–steppe carbon dynamics, we use a highly resolved, multiproxy, palaeolimnological approach, based on sediment records from Lake Baikal. We reconstruct proxies that are relevant to understanding carbon dynamics including carbon mass accumulation rates (CMAR; g C m−2 yr−1) and isotope composition of organic matter (δ13CTOC). Forest–steppe dynamics were reconstructed using pollen, and diatom records provided measures of primary production from near- and off-shore communities. We used a generalized additive model (GAM) to identify significant change points in temporal series, and by applying generalized linear least-squares regression modelling to components of the multiproxy data, we address (1) What factors influence carbon dynamics during early Holocene warming and late Holocene cooling? (2) How did carbon dynamics respond to abrupt sub-Milankovitch scale events? and (3) What is the Holocene carbon storage budget for Lake Baikal. CMAR values range between 2.8 and 12.5 g C m−2 yr−1. Peak burial rates (and greatest variability) occurred during the early Holocene, associated with melting permafrost and retreating glaciers, while lowest burial rates occurred during the neoglacial. Significant shifts in carbon dynamics at 10.3, 4.1 and 2.8 kyr bp provide compelling evidence for the sensitivity of the region to sub-Milankovitch drivers of climate change. We estimate that 1.03 Pg C was buried in Lake Baikal sediments during the Holocene, almost one-quarter of which was buried during the early Holocene alone. Combined, our results highlight the importance of understanding the close linkages between carbon cycling and hydrological processes, not just temperatures, in southern Siberian environments

Rapid and highly variable warming of lake surface waters around the globe

peer reviewedIn this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade-1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors - from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade-1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade-1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes. © 2015. American Geophysical Union. All Rights Reserved

Rapid and highly variable warming of lake surface waters around the globe

Peer reviewed. ©2015. The Authors.This is an open access article under theterms of the Creative CommonsAttribution-NonCommercial-N oDerivsLicense, which permits use and distri-bution in any medium, provided theoriginal work is properly cited, the use isnon-commerc ial and no modificationsor adaptations are made.In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade 1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors —from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade 1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade 1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes

Rapid and highly variable warming of lake surface waters around the globe

In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade-1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors - from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade-1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade-1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes

The rise and fall of plankton: long-term changes in the vertical distribution of algae and grazers in Lake Baikal, Siberia

Both surface water temperatures and the intensity of thermal stratification have increased recently in large lakes throughout the world. Such physical changes can be accompanied by shifts in plankton community structure, including changes in relative abundances and depth distributions. Here we analyzed 45 years of data from Lake Baikal, the world's oldest, deepest, and most voluminous lake, to assess long-term trends in the depth distribution of pelagic phytoplankton and zooplankton. Surface water temperatures in Lake Baikal increased steadily between 1955 and 2000, resulting in a stronger thermal gradient within the top 50 m of the water column. In conjunction with these physical changes our analyses reveal significant shifts in the daytime depth distribution of important phytoplankton and zooplankton groups. The relatively heavy diatoms, which often rely on mixing to remain suspended in the photic zone, shifted downward in the water column by 1.90 m y(-1), while the depths of other phytoplankton groups did not change significantly. Over the same time span the density-weighted average depth of most major zooplankton groups, including cladocerans, rotifers, and immature copepods, exhibited rapid shifts toward shallower positions (0.57-0.75 m y(-1)). As a result of these depth changes the vertical overlap between herbivorous copepods (Epischura baikalensis) and their algal food appears to have increased through time while that for cladocerans decreased. We hypothesize that warming surface waters and reduced mixing caused these ecological changes. Future studies should examine how changes in the vertical distribution of plankton might impact energy flow in this lake and others

The temporal relationships and correlation structures of <i>Φ</i>(<i>t</i>,<i>n</i>) and the Global-SST ENSO index across the history of the PDO index from 1946 since 1946.

<p>(A) Plot of monthly <i>Φ</i>(<i>t</i>,40) time series (Blue) with the monthly Global-SST ENSO index (Red) from 1946–2004. The Global-SST ENSO index captures the low-frequency components of other, location specific ENSO indices. The data were continuous from January 1946 to December 2003. Global-SST ENSO is presented as raw, unfiltered values (points) and smoothed to produce similar high frequency contributions to <i>Φ</i>(<i>t</i>,40) (line) (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0014688#s3" target="_blank">Methods</a>). The periods 1957–1964, 1976–1988 and 1992–1998 are PDO “warm” phases and are indicated in gray, the intervals are PDO “cool” periods. (B and C) Plots of the Global-SST ENSO index plotted against <i>Φ</i>(<i>t</i>,40). Data were pre-whitened to reduce autocorrelation for analysis. Cross-correlation coefficients of determination (displayed) were estimated for the entire periods indicated. Data are plotted at the lag that produced the greatest cross-correlation coefficient magnitude to convey the strength of the relationship. The mean cross-correlation coefficient (<i>r</i>) for the PDO cool periods (B) was 0.67 at an average lag of 3. 5 months with ENSO leading <i>Φ</i>(<i>t</i>,40).</p

The values of <i>Φ</i>(<i>t</i>,<i>n</i>) over a range of frequency scales and across the time series from 1948 to 2004.

<p>(A and B) Assembled values of <i>Φ</i>(<i>t</i>,<i>n</i>) from long term Lake Baikal surface temperature time series over the period 1948 to 2003 and window sizes (<i>n</i>) 36 to 276 months. Cooler colors are more negative <i>Φ</i>(<i>t</i>,n); warmer colors are more positive <i>Φ</i>(<i>t</i>,<i>n</i>); if phase were a constant, the surface would be flat. The surface tapers with increasing <i>n</i> as <i>Φ</i>(<i>t</i>,<i>n</i>) is referenced to the center of the window of length <i>n</i>, and as <i>n</i> increases there is an increasing <i>n</i>/2-long segment that does not have a relevant measure of <i>Φ</i>(<i>t</i>,<i>n</i>) at the beginning and end of the time series. (C, D and E) Time series of <i>Φ</i>(<i>t</i>,<i>n</i>) sampled at <i>n</i> equal 40 (C), 92 (D) and 192 (E) months. Estimating <i>Φ</i>(<i>t</i>,<i>n</i>) at longer <i>n</i> averages over a longer time and is equivalent to smoothing the low <i>n Φ</i>(<i>t</i>,<i>n</i>) time series. As such <i>Φ</i>(<i>t</i>,<i>n</i>) at lower values of <i>n</i> captures temperature anomalies occurring at higher frequencies and vice versa.</p