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Interests

 

My research is broadly focused on climate dynamics and global climate change. My work spans a range of subjects, including sea ice, polar climate, the hydrological cycle, and the ocean circulation. The ultimate goal of my research is to develop a better understanding of the processes that shape Earth's climate and its response to external forcing, with a particular focus on how constituent elements of the surface, including the oceans, crysophere, and land, interact with the atmosphere and each other. I use a range of tools and techniques including comprehensive Earth system models, targeted experiments in climate models of varying complexity, conceptual models that provide simplified representations of underlying physical processes, and advanced statistical methods. The field of climate dynamics is inherently interdisciplinary, as the atmosphere, oceans, cryosphere, and land surface are intimately coupled, and affect Earth’s climate on timescales ranging from seasons to millennia. I enjoy working and collaborating on research questions that are at the intersection of these components.

Climate dynamics and global climate change

At a global scale, climate change is set by interactions between climate forcings, climate feedbacks, and ocean heat uptake, while at regional scales, atmospheric energy transport and other processes become important. I am interested in the relative importance of these processes and how energy balance models or simple energetic frameworks can be used to infer processes that influence polar-amplified warming, geographical shifts in tropical rainfall, the magnitude of transient warming, or land-sea contrasts. My recent and ongoing work examines: the influence of continental land configurations on the climate response; mechanisms of ocean heat uptake; anthropogenic fingerprints on extreme temperature changes; and sources of uncertainty in the pattern of warming.

Relevant publications

  • Bonan, D.B., K.C. Armour, G.H. Roe, N. Siler, and N. Feldl (2018): Sources of uncertainty in the meridional pattern of climate change.​ Geophysical Research Letters, 45 (17), 9131-9140. doi: 10.1029/2018GL079429

  • Bonan, D.B., A.F. Thompson, T. Schneider, and L. Zanna (in preparation): A conceptual model of the coupled ocean-atmosphere system.

  • Bonan, D.B., M.M. Laguë, and W.R. Boos (in preparation): Effects of continental land distribution on the climate response to greenhouse-gas forcing.

  • Patel, R., T. Schneider, and D.B. Bonan (in preparation): Anthropogenic signatures on observed temperature extremes.

Sea ice

Sea ice is a fundamental component of the climate system, influencing Earth's energy balance and atmospheric and oceanic circulations. Both Arctic and Antarctic sea ice have undergone striking changes over the past few decades and are projected to continue to change throughout the next century. One of the goals of my research is to identify processes that control the short- and long- term evolution of sea ice and explain how the sea ice cover in both hemispheres interacts with the atmosphere and oceans. I am also broadly interested in the predictability of sea ice and improving the representation of sea ice in climate models. Recent and ongoing work examines: constraints on Arctic sea ice loss, sources of low-frequency sea ice variability, and mechanisms of seasonal Arctic sea-ice predictability.

Relevant publications

  • Bonan, D.B., M. Bushuk, and M. Winton (2019): A spring barrier for regional predictions of summer Arctic sea ice. Geophysical Research Letters, 46 (11), 5937-5947. doi: 10.1029/2019GL082947
     

  • Bushuk, M., M. Winton, D.B. Bonan, E. Blanchard-Wrigglesworth, and T. Delworth (2020): A mechanism for the Arctic sea ice spring predictability barrier. Geophysical Research Letters, 47 (13), e2020GL088335. doi: 10.1029/2020GL088335

  • Bonan, D.B., F. Lehner, and M.M. Holland (2021): Partitioning uncertainty in projections of Arctic sea ice. Environmental Research Letters, 16 (4), 044002. doi: 10.1088/1748-9326/ABE0EC

  • Bonan, D.B., T. Schneider, I. Eisenman, and R.C.J. Wills (2021): Constraining the date of a seasonally ice-free Arctic using a simple model. Geophysical Research Letters, 48 (18), e2021GL094309. doi: 10.1029/2020GL094309

  • Dörr, J., D.B. Bonan, M. Årthun, L. Svendsen, and R.C.J Wills (2023): Forced and internal components of observed Arctic sea-ice changes. The Cryosphere, 17 (9), 4133-4153. doi: 10.5194/TC-17-4133-2023

  • ​Bonan, D.B., J. Dörr, R.C.J. Wills, A.F. Thompson, and M. Årthun (submitted): Sources of low-frequency variability in observed Antarctic sea ice. The Cryosphere.

Polar climate

Polar climate dynamics are controlled by both radiative and non-radiative interactions between the atmosphere, oceans, sea ice, ice sheets, and land surfaces. The polar regions are thus highly sensitive to changes in climate forcing and exhibit large internal variability. I am interested in how surface processes in the cyrosphere, oceans, and land interact with the atmosphere to shape polar climate change. My recent and ongoing work examines: mechanisms for long-term surface temperature trends; mechanisms for abrupt sea ice and temperature changes; and contributions to high-latitude precipitation change under warming.

Relevant publications

  • Bonan, D.B., N. Feldl, M.D. Zelinka, and L.C. Hahn (2023): Contributions to regional precipitation change and its polar-amplified pattern under warming. Environmental Research: Climate, 2 (3), 035010. doi: 10.1088/2752-5295/ACE27A

  • Wilson, E.A., D.B. Bonan, A.F. Thompson, N. Armstrong, and S.C. Riser (2023): Mechanisms for abrupt summertime circumpolar surface warming in the Southern Ocean. Journal of Climate, 36 (20), 7025-7039. doi: 10.1175/JCLI-D-22-0501.1

  • Dong, Y., L.M. Polvani, and D.B. Bonan (2023): Recent multi-decadal Southern Ocean surface cooling unlikely caused by Southern Annular Mode trends. Geophysical Research Letters. xx (xx), e2023GL106142. doi: 10.1029/2023GL106142

Hydrological cycle

The hydrological cycle is a crucial component of the climate system, affecting the formation of water masses in the ocean and the amount of runoff or availability of water over the land, which can impact soil moisture, drought, flooding, and wildfires. I am interested in the processes that shape the large-scale patterns of precipitation, evaporation, and relative humidity, including how energetic frameworks can be used to constrain features of the atmospheric circulation or land surface processes. Recent and ongoing work examines: the response of the hydrological cycle to global warming in an energy balance model; the influence of climate feedbacks on regional hydrological changes; and the dynamic and thermodynamic components of regional hydrological changes.

Relevant publications

  • Bonan, D.B., N. Siler, G.H. Roe, and K.C. Armour (2023): Energetic constraints on the pattern of changes to the hydrological cycle under global warming. Journal of Climate, 36 (10), 3499-3522. doi: 10.1175/JCLI-D-22-0337.1

  • Siler, N., D.B. Bonan, and A. Donohoe (2023): Diagnosing mechanisms of hydrologic change under global warming in the CESM1 Large Ensemble. Journal of Climate, 36 (23), 8243-8257. doi: 10.1175/JCLI-D-23-0086.1

  • Bonan, D.B., N. Feldl, N. Siler, J.E. Kay, K.C. Armour, I. Eisenman, and G.H. Roe (submitted): The influence of climate feedbacks on regional hydrological changes under global warming. ​​Geophysical Research Letters.

  • Bonan, D.B., and T. Schneider (in preparation): Controls on the transient and equilibrium global hydrological sensitivity under greenhouse-gas forcing.

  • Bonan, D.B., T. Schneider, J. Zhu, and T. Mauritsen (in preparation): Global and regional precipitation in extremely warm climates simulated with comprehensive GCMs.

Ocean circulation

The ocean's global overturning circulation regulates Earth's climate by transporting heat between hemispheres, influencing the rate of ocean heat and carbon uptake, and ventilating the interior of the ocean. Sparse observations necessitates the use of conceptual models that help to reveal primary controls on the ocean's deep stratification and overturning circulation. I am interested in understanding the processes that control the short- and long-term evolution of the ocean circulation. My recent and ongoing work examines: how the ocean's global overturning circulation responds to warming on centennial-to-millennial timescales; constraints on the strength of the ocean's global overturning circulation; and the role of low-latitude surface forcing in transitions of the oceans's global overturning circulation in past climates.

Relevant publications

  • Bonan, D.B., A.F. Thompson, E.R. Newsom, S. Sun, and M. Rugenstein (2022): Transient and equilibrium responses of the Atlantic overturning circulation to warming in coupled climate models: the role of temperature and salinity. Journal of Climate, 35 (15), 5173-5193. doi: 10.1175/JCLI-D-21-0912.1

  • Nayak, M., D.B. Bonan, E.R. Newsom, and A.F. Thompson (in preparation): Controls on the strength of the climatological Atlantic meridional overturning circulation in coupled climate models.

  • Bonan, D.B., A.F. Thompson, T. Schneider, L. Zanna, K.C. Armour, and S. Sun (in preparation): Constraints on weakening of the Atlantic meridional overturning circulation over the 21st century.

  • Bonan, D.B., A.F. Thompson, T. Schneider, and L. Zanna (in preparation): Transient and equilibrium responses of the ocean's overturning circulation to climate change: insights from a conceptual model. 

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